drm/msm/dp: Initialize dp->aux->drm_dev before registration

Avoids the following WARN:
[    3.009556] ------------[ cut here ]------------
[    3.014306] WARNING: CPU: 7 PID: 109 at
drivers/gpu/drm/drm_dp_helper.c:1796 drm_dp_aux_register+0xa4/0xac
[    3.024209] Modules linked in:
[    3.027351] CPU: 7 PID: 109 Comm: kworker/7:8 Not tainted 5.10.47 #69
[    3.033958] Hardware name: Google Lazor (rev1 - 2) (DT)
[    3.039323] Workqueue: events deferred_probe_work_func
[    3.044596] pstate: 60c00009 (nZCv daif +PAN +UAO -TCO BTYPE=--)
[    3.050761] pc : drm_dp_aux_register+0xa4/0xac
[    3.055329] lr : dp_aux_register+0x40/0x88
[    3.059538] sp : ffffffc010ad3920
[    3.062948] x29: ffffffc010ad3920 x28: ffffffa64196ac70
[    3.067239] mmc1: Command Queue Engine enabled
[    3.068406] x27: ffffffa64196ac68 x26: 0000000000000001
[    3.068407] x25: 0000000000000002 x24: 0000000000000060
[    3.068409] x23: ffffffa642ab3400 x22: ffffffe126c10e5b
[    3.068410] x21: ffffffa641dc3188 x20: ffffffa641963c10
[    3.068412] x19: ffffffa642aba910 x18: 00000000ffff0a00
[    3.068414] x17: 000000476f8e002a x16: 00000000000000b8
[    3.073008] mmc1: new HS400 Enhanced strobe MMC card at address 0001
[    3.078448] x15: ffffffffffffffff x14: ffffffffffffffff
[    3.078450] x13: 0000000000000030 x12: 0000000000000030
[    3.078452] x11: 0101010101010101 x10: ffffffe12647a914
[    3.078453] x9 : ffffffe12647a8cc x8 : 0000000000000000
[    3.084452] mmcblk1: mmc1:0001 DA4032 29.1 GiB
[    3.089372]
[    3.089372] x7 : 6c6064717372fefe x6 : ffffffa642b11494
[    3.089374] x5 : 0000000000000000 x4 : 6d006c657869ffff
[    3.089375] x3 : 000000006c657869 x2 : 000000000000000c
[    3.089376] x1 : ffffffe126c3ae3c x0 : ffffffa642aba910
[    3.089381] Call trace:
[    3.094931] mmcblk1boot0: mmc1:0001 DA4032 partition 1 4.00 MiB
[    3.100291]  drm_dp_aux_register+0xa4/0xac
[    3.100292]  dp_aux_register+0x40/0x88
[    3.100294]  dp_display_bind+0x64/0xcc
[    3.100295]  component_bind_all+0xdc/0x210
[    3.100298]  msm_drm_bind+0x1e8/0x5d4
[    3.100301]  try_to_bring_up_master+0x168/0x1b0
[    3.105861] mmcblk1boot1: mmc1:0001 DA4032 partition 2 4.00 MiB
[    3.112282]  __component_add+0xa0/0x158
[    3.112283]  component_add+0x1c/0x28
[    3.112284]  dp_display_probe+0x33c/0x380
[    3.112286]  platform_drv_probe+0x9c/0xbc
[    3.112287]  really_probe+0x140/0x35c
[    3.112289]  driver_probe_device+0x84/0xc0
[    3.112292]  __device_attach_driver+0x94/0xb0
[    3.117967] mmcblk1rpmb: mmc1:0001 DA4032 partition 3 16.0 MiB,
chardev (239:0)
[    3.123201]  bus_for_each_drv+0x8c/0xd8
[    3.123202]  __device_attach+0xc4/0x150
[    3.123204]  device_initial_probe+0x1c/0x28
[    3.123205]  bus_probe_device+0x3c/0x9c
[    3.123206]  deferred_probe_work_func+0x90/0xcc
[    3.123211]  process_one_work+0x218/0x3ec
[    3.131976]  mmcblk1: p1 p2 p3 p4 p5 p6 p7 p8 p9 p10 p11 p12
[    3.134123]  worker_thread+0x288/0x3e8
[    3.134124]  kthread+0x148/0x1b0
[    3.134127]  ret_from_fork+0x10/0x30
[    3.134128] ---[ end trace cfb9fce3f70f824d ]---

Signed-off-by: Sean Paul <seanpaul@chromium.org>
Reviewed-by: Abhinav Kumar <abhinavk@codeaurora.org>
Link: https://lore.kernel.org/r/20210714152910.55093-1-sean@poorly.run


Signed-off-by: Rob Clark <robdclark@chromium.org>