drm/amdkfd: Remove unnecessary pm_init() for non HWS mode

drm/amdkfd: Remove unnecessary pm_init() for non HWS mode

The packet manager is not needed for non HWS mode except Hawaii, so only
initialize it for Hawaii under non HWS mode. This will simplify debugging
under non HWS mode for all new asics, because it eliminates one variable
out of the equation in non HWS mode

Signed-off-by: Yong Zhao <Yong.Zhao@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>