drm/amdgpu/userq: dont lock root bo with userq_mutex held

drm/amdgpu/userq: dont lock root bo with userq_mutex held

Do not hold reservation lock for root bo if userq_mutex
is already held in the call flow this cause a lock
issue with ttm_bo_delayed_delete.

Its better to lock the vm->root.bo first and then go ahead
with userq_mutex so userq_mutex threads dont get stuck until
the reservation lock is held.

In this case it helps in the function amdgpu_userq_buffer_vas_mapped
for each queue during restore_all.

Signed-off-by: Sunil Khatri <sunil.khatri@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>