drm/amdgpu/userq: Fix the mutex_init cleanup for fence_drv_lock

drm/amdgpu/userq: Fix the mutex_init cleanup for fence_drv_lock

mutex fence_drv_lock is destroyed in amdgpu_userq_fence_driver_free
also in one of the jump condition mutex_destroy is also called leading
to double mutex_destroy.

So rearranging the code so amdgpu_userq_fence_driver_free takes care
of the clean up along with mutex_destroy.

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>