drm/amdkfd: suspend scheduler during PTL re-enabling

drm/amdkfd: suspend scheduler during PTL re-enabling

Stop the scheduler before releasing the PTL disable request to ensure
the GPU is quiescent during the PTL state transition. This prevents
potential queue preemption failures and GPU resets caused by modifying
PTL state while waves are executing

v1->v2:
only stop/start the scheduler when the PTL state actually needs to transition(Yifan)

Signed-off-by: Perry Yuan <perry.yuan@amd.com>
Reviewed-by: Yifan Zhang <yifan1.zhang@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>