drm/v3d: Add a note about OOM vs FLDONE, which may be racing on v3.3.

We deref v3d->bin_job in the work handler, but v3d->bin_job doesn't
actually hold a ref on the job.

v2: typo fix FRDONE -> FLDONE
Signed-off-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20190313235211.28995-1-eric@anholt.netReviewed-by: Dave Emett <david.emett@broadcom.com>

drivers/gpu/drm/v3d/v3d_irq.c

@@ -87,7 +87,8 @@ v3d_irq(int irq, void *arg)
 	if (intsts & V3D_INT_OUTOMEM) {
 		/* Note that the OOM status is edge signaled, so the
 		 * interrupt won't happen again until the we actually
-		 * add more memory.
+		 * add more memory.  Also, as of V3D 4.1, FLDONE won't
+		 * be reported until any OOM state has been cleared.
 		 */
 		schedule_work(&v3d->overflow_mem_work);
 		status = IRQ_HANDLED;