drm/amdkfd: Free gang_ctx_bo and wptr_bo in pqm_uninit

[Why]
Memory leaks of gang_ctx_bo and wptr_bo.

[How]
Free gang_ctx_bo and wptr_bo in pqm_uninit.

v2: add a common function pqm_clean_queue_resource to
free queue's resources.
v3: reset pdd->pqd.num_gws when destorying GWS queue.

Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: ZhenGuo Yin <zhenguo.yin@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>