drm/amd/pm: skip setting gfx cgpg in the s0ix suspend-resume

drm/amd/pm: skip setting gfx cgpg in the s0ix suspend-resume

[ Upstream commit 8c45096c60d6ce6341c374636100ed1b2c1c33a1 ]

In the s0ix entry need retain gfx in the gfxoff state,so here need't
set gfx cgpg in the S0ix suspend-resume process. Moreover move the S0ix
check into SMU12 can simplify the code condition check.

Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/1712
Signed-off-by: Prike Liang <Prike.Liang@amd.com>
Reviewed-by: Evan Quan <evan.quan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>