drm/msm: Verify that MSM_SUBMIT_BO_FLAGS are set

For every submission buffer object one of MSM_SUBMIT_BO_WRITE
and MSM_SUBMIT_BO_READ must be set (and nothing else). If we
allowed zero then the buffer object would never get queued to
be unreferenced.

Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>