imx: mx6: Fix incorrect clear mmdc_ch0 handshake mask

Since the MX6UL/SL/SX only has one DDR channel, in CCM_CCDR register
the bit[17] for mmdc_ch0 is reserved and its proper state should be 1.
When clear this bit, the periph_clk_sel cannot be set and that
CDHIPR[periph_clk_sel_busy] handshake never clears.
Signed-off-by: NYe Li <ye.li@nxp.com>
Signed-off-by: NPeng Fan <van.freenix@gmail.com>
Acked-by: NStefano Babic <sbabic@denx.de>

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

@@ -278,7 +278,10 @@ static void clear_mmdc_ch_mask(void)
 	reg = readl(&mxc_ccm->ccdr);
 
 	/* Clear MMDC channel mask */
-	reg &= ~(MXC_CCM_CCDR_MMDC_CH1_HS_MASK | MXC_CCM_CCDR_MMDC_CH0_HS_MASK);
+	if (is_cpu_type(MXC_CPU_MX6SX) || is_cpu_type(MXC_CPU_MX6UL) || is_cpu_type(MXC_CPU_MX6SL))
+		reg &= ~(MXC_CCM_CCDR_MMDC_CH1_HS_MASK);
+	else
+		reg &= ~(MXC_CCM_CCDR_MMDC_CH1_HS_MASK | MXC_CCM_CCDR_MMDC_CH0_HS_MASK);
 	writel(reg, &mxc_ccm->ccdr);
 }