drm/gud: Add GUD_PIXEL_FORMAT_R8

commit 07fee7e123c16349ad5a8d94fb0bf1822d7ee0e1 from
https://nv-tegra.nvidia.com/r/3rdparty/canonical/linux-jammy.git jetson_36.3

Add support for 8-bit greyscale format.

Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210929191201.34456-5-noralf@tronnes.org
(cherry picked from commit 4cabfedc

)
Change-Id: I5f70078713052cbdef60af73042fdbc1883f5fd7
Signed-off-by: Thierry Reding <treding@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/c/3rdparty/canonical/linux-jammy/+/2985820
Reviewed-by: svcacv <svcacv@nvidia.com>
Reviewed-by: Jonathan Hunter <jonathanh@nvidia.com>
GVS: Gerrit_Virtual_Submit <buildbot_gerritrpt@nvidia.com>
Signed-off-by: Rajeshkumar Ramasamy <rajeshkumar.ramasamy@windriver.com>