drm/amdgpu: userq_va_mapped should remain true once done

drm/amdgpu: userq_va_mapped should remain true once done

Multiple queues needs these bo_va objects belonging to
the same uq_mgr. So once they are mapped lets not unmap
them as at any point of time any of the queues might be
using it.

Also userq_va_mapped should be a boolean than atomic.

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>