MX6 SabreSD: Use readl() to read the CCM_CCGR3 register

Align with the context to use readl() to read the CCM_CCGR3
register with memory barrier instead of __raw_readl().
Signed-off-by: NLiu Ying <Ying.Liu@freescale.com>
Reviewed-by: NFabio Estevam <fabio.estevam@freescale.com>

board/freescale/mx6sabresd/mx6sabresd.c

@@ -390,7 +390,7 @@ static void setup_display(void)
 	imx_setup_hdmi();
 
 	/* Turn on LDB0, LDB1, IPU,IPU DI0 clocks */
-	reg = __raw_readl(&mxc_ccm->CCGR3);
+	reg = readl(&mxc_ccm->CCGR3);
 	reg |=  MXC_CCM_CCGR3_LDB_DI0_MASK | MXC_CCM_CCGR3_LDB_DI1_MASK;
 	writel(reg, &mxc_ccm->CCGR3);