drm/amdgpu/sdma: fix engine reset handling

Move the kfd suspend/resume code into the caller.  That
is where the KFD is likely to detect a reset so on the KFD
side there is no need to call them.  Also add a mutex to
lock the actual reset sequence.

v2: make the locking per instance

Fixes: bac38ca8 ("drm/amdkfd: implement per queue sdma reset for gfx 9.4+")
Reviewed-by: Jesse Zhang <jesse.zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>