accel: fix CONFIG_DRM dependencies

At the moment, accel drivers can be built-in even with CONFIG_DRM=m,
but this causes a link failure:

x86_64-linux-ld: drivers/accel/ivpu/ivpu_drv.o: in function `ivpu_dev_init':
ivpu_drv.c:(.text+0x1535): undefined reference to `drmm_kmalloc'
x86_64-linux-ld: ivpu_drv.c:(.text+0x1562): undefined reference to `drmm_kmalloc'
x86_64-linux-ld: drivers/accel/ivpu/ivpu_drv.o: in function `ivpu_remove':
ivpu_drv.c:(.text+0x1faa): undefined reference to `drm_dev_unregister'
x86_64-linux-ld: drivers/accel/ivpu/ivpu_drv.o: in function `ivpu_probe':
ivpu_drv.c:(.text+0x1fef): undefined reference to `__devm_drm_dev_alloc'

The problem is that DRM_ACCEL is a 'bool' symbol, so driver that
only depend on DRM_ACCEL but not also on DRM do not see the restriction
to =m configs.

To ensure that each accel driver has an implied dependency on CONFIG_DRM,
enclose the entire Kconfig file in an if/endif check.

Fixes: 8bf48897 ("drivers/accel: define kconfig and register a new major")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Stanislaw Gruszka <stanislaw.gruszka@linux.intel.com>
Reviewed-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Jacek Lawrynowicz <jacek.lawrynowicz@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230127221504.2522909-1-arnd@kernel.org