drm/amd/display: Restore backlight brightness after system resume

Laptops with AMD APU doesn't restore display backlight brightness after
system resume.

This issue started when DC was introduced.

Let's use BL_CORE_SUSPENDRESUME so the backlight core calls
update_status callback after system resume to restore the backlight
level.

Tested on Dell Inspiron 3180 (Stoney Ridge) and Dell Latitude 5495
(Raven Ridge).

Cc: <stable@vger.kernel.org>
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -2113,6 +2113,7 @@ static int amdgpu_dm_backlight_get_brightness(struct backlight_device *bd)
 }
 
 static const struct backlight_ops amdgpu_dm_backlight_ops = {
+	.options = BL_CORE_SUSPENDRESUME,
 	.get_brightness = amdgpu_dm_backlight_get_brightness,
 	.update_status	= amdgpu_dm_backlight_update_status,
 };