drm/amdgpu/sdma5.2: add begin/end_use ring callbacks

Add begin/end_use ring callbacks to disallow GFXOFF when
SDMA work is submitted and allow it again afterward.

This should avoid corner cases where GFXOFF is erroneously
entered when SDMA is still active.  For now just allow/disallow
GFXOFF in the begin and end helpers until we root cause the
issue.  This should not impact power as SDMA usage is pretty
minimal and GFXOSS should not be active when SDMA is active
anyway, this just makes it explicit.

v2: move everything into sdma5.2 code.  No reason for this
to be generic at this point.
v3: Add comments in new code

Link: https://gitlab.freedesktop.org/drm/amd/-/issues/2220


Reviewed-by: Mario Limonciello <mario.limonciello@amd.com> (v1)
Tested-by: Mario Limonciello <mario.limonciello@amd.com> (v1)
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org # 5.15+