drm/amd/pm: avoid duplicate powergate/ungate setting

Just bail out if the target IP block is already in the desired
powergate/ungate state. This can avoid some duplicate settings
which sometimes may cause unexpected issues.

Link: https://lore.kernel.org/all/YV81vidWQLWvATMM@zn.tnic/
Bug: https://bugzilla.kernel.org/show_bug.cgi?id=214921
Bug: https://bugzilla.kernel.org/show_bug.cgi?id=215025
Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/1789


Signed-off-by: Evan Quan <evan.quan@amd.com>
Tested-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>