MLK-11159-2 Revert "MLK-11028 imx: mx6qp change L2 prefetch offset to 0"

This reverts commit 2bc93d766d.

After further investigation, find L2 prefetch offset setting of 0xF is not the
root cause for USB stress reboot failure. With the fix in USB driver,
and L2 prefetch offset setting of 0xF, the reboot stress test has passed 4-days
both on imx6q and imx6qp sabreauto board.

Signed-off-by: Robby Cai <r63905@freescale.com>

arch/arm/cpu/armv7/mx6/soc.c

@@ -1075,7 +1075,7 @@ void v7_outer_cache_enable(void)
 
 	/* Turn on the L2 I/D prefetch, double linefill */
 	/* Set prefetch offset with any value except 23 as per errata 765569 */
-	val |= 0x70000000;
+	val |= 0x7000000f;
 
 	/*
 	 * The L2 cache controller(PL310) version on the i.MX6D/Q is r3p1-50rel0