freedreno/a5xx: fix random faults on first sysmem draw

Not sure what this event is, but blob writes it.. and it seems to solve
random write faults at mystery address that would sometimes happen on
first BYPASS draw.

Signed-off-by: Rob Clark <robdclark@gmail.com>
diff --git a/src/gallium/drivers/freedreno/a5xx/fd5_gmem.c b/src/gallium/drivers/freedreno/a5xx/fd5_gmem.c
index cf1cd76..775d5b9 100644
--- a/src/gallium/drivers/freedreno/a5xx/fd5_gmem.c
+++ b/src/gallium/drivers/freedreno/a5xx/fd5_gmem.c
@@ -485,6 +485,9 @@
 	OUT_PKT7(ring, CP_SKIP_IB2_ENABLE_GLOBAL, 1);
 	OUT_RING(ring, 0x0);
 
+	OUT_PKT7(ring, CP_EVENT_WRITE, 1);
+	OUT_RING(ring, UNK_19);
+
 	OUT_PKT4(ring, REG_A5XX_PC_POWER_CNTL, 1);
 	OUT_RING(ring, 0x00000003);   /* PC_POWER_CNTL */