freedreno/a5xx: fix missing restore state

RB_CLEAR_CNTL seems to be in a funny state after boot (at least on
8x96/a530).

Cc: 17.2 <mesa-stable@lists.freedesktop.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>

src/gallium/drivers/freedreno/a5xx/fd5_emit.c

@@ -1048,6 +1048,9 @@ t7              opcode: CP_WAIT_FOR_IDLE (26) (1 dwords)
 	OUT_RING(ring, 0x00000000);
 	OUT_RING(ring, 0x00000000);
 	OUT_RING(ring, 0x00000000);
+
+	OUT_PKT4(ring, REG_A5XX_RB_CLEAR_CNTL, 1);
+	OUT_RING(ring, 0x00000000);
 }
 
 static void