drm/amd: Forbid suspending into non-default suspend states

On systems that default to 'deep' some userspace software likes
to try to suspend in 'deep' first.  If there is a failure for any
reason (such as -ENOMEM) the failure is ignored and then it will
try to use 's2idle' as a fallback. This fails, but more importantly
it leads to graphical problems.

Forbid this behavior and only allow suspending in the last state
supported by the system.

Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4093


Acked-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://lore.kernel.org/r/20250408180957.4027643-1-superm1@kernel.org


Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>