drm/probe_helper: sort out poll_running vs poll_enabled

There are two flags attemting to guard connector polling:
poll_enabled and poll_running. While poll_enabled semantics is clearly
defined and fully adhered (mark that drm_kms_helper_poll_init() was
called and not finalized by the _fini() call), the poll_running flag
doesn't have such clearliness.

This flag is used only in drm_helper_probe_single_connector_modes() to
guard calling of drm_kms_helper_poll_enable, it doesn't guard the
drm_kms_helper_poll_fini(), etc. Change it to only be set if the polling
is actually running. Tie HPD enablement to this flag.

This fixes the following warning reported after merging the HPD series:

Hot plug detection already enabled
WARNING: CPU: 2 PID: 9 at drivers/gpu/drm/drm_bridge.c:1257 drm_bridge_hpd_enable+0x94/0x9c [drm]
Modules linked in: videobuf2_memops snd_soc_simple_card snd_soc_simple_card_utils fsl_imx8_ddr_perf videobuf2_common snd_soc_imx_spdif adv7511 etnaviv imx8m_ddrc imx_dcss mc cec nwl_dsi gov
CPU: 2 PID: 9 Comm: kworker/u8:0 Not tainted 6.2.0-rc2-15208-g25b283acd578 #6
Hardware name: NXP i.MX8MQ EVK (DT)
Workqueue: events_unbound deferred_probe_work_func
pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : drm_bridge_hpd_enable+0x94/0x9c [drm]
lr : drm_bridge_hpd_enable+0x94/0x9c [drm]
sp : ffff800009ef3740
x29: ffff800009ef3740 x28: ffff000009331f00 x27: 0000000000001000
x26: 0000000000000020 x25: ffff800001148ed8 x24: ffff00000a8fe000
x23: 00000000fffffffd x22: ffff000005086348 x21: ffff800001133ee0
x20: ffff00000550d800 x19: ffff000005086288 x18: 0000000000000006
x17: 0000000000000000 x16: ffff8000096ef008 x15: 97ffff2891004260
x14: 2a1403e194000000 x13: 97ffff2891004260 x12: 2a1403e194000000
x11: 7100385f29400801 x10: 0000000000000aa0 x9 : ffff800008112744
x8 : ffff000000250b00 x7 : 0000000000000003 x6 : 0000000000000011
x5 : 0000000000000000 x4 : ffff0000bd986a48 x3 : 0000000000000001
x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff000000250000
Call trace:
 drm_bridge_hpd_enable+0x94/0x9c [drm]
 drm_bridge_connector_enable_hpd+0x2c/0x3c [drm_kms_helper]
 drm_kms_helper_poll_enable+0x94/0x10c [drm_kms_helper]
 drm_helper_probe_single_connector_modes+0x1a8/0x510 [drm_kms_helper]
 drm_client_modeset_probe+0x204/0x1190 [drm]
 __drm_fb_helper_initial_config_and_unlock+0x5c/0x4a4 [drm_kms_helper]
 drm_fb_helper_initial_config+0x54/0x6c [drm_kms_helper]
 drm_fbdev_client_hotplug+0xd0/0x140 [drm_kms_helper]
 drm_fbdev_generic_setup+0x90/0x154 [drm_kms_helper]
 dcss_kms_attach+0x1c8/0x254 [imx_dcss]
 dcss_drv_platform_probe+0x90/0xfc [imx_dcss]
 platform_probe+0x70/0xcc
 really_probe+0xc4/0x2e0
 __driver_probe_device+0x80/0xf0
 driver_probe_device+0xe0/0x164
 __device_attach_driver+0xc0/0x13c
 bus_for_each_drv+0x84/0xe0
 __device_attach+0xa4/0x1a0
 device_initial_probe+0x1c/0x30
 bus_probe_device+0xa4/0xb0
 deferred_probe_work_func+0x90/0xd0
 process_one_work+0x200/0x474
 worker_thread+0x74/0x43c
 kthread+0xfc/0x110
 ret_from_fork+0x10/0x20
---[ end trace 0000000000000000 ]---

Reported-by: Laurentiu Palcu <laurentiu.palcu@oss.nxp.com>
Fixes: c8268795 ("drm/probe-helper: enable and disable HPD on connectors")
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Chen-Yu Tsai <wenst@chromium.org>
Acked-by: Laurentiu Palcu <laurentiu.palcu@oss.nxp.com>
Tested-by: Laurentiu Palcu <laurentiu.palcu@oss.nxp.com>
Tested-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230124104548.3234554-2-dmitry.baryshkov@linaro.org