iomux-v3: Add support for mx6sl LVE bit

On mx6sl there is a LVE (Low Voltage Enable) bit in the IOMUXC_SW_PAD_CTL
register that can enable or disable low voltage on the pad.

LVE is bit 22 of IOMUXC_SW_PAD_CTL register, but in order to make the
calculation easier we can define it as a flag in bit 1, since this bit is unused.

Add support for it.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Tested-by: Otavio Salvador <otavio@ossystems.com.br>
diff --git a/arch/arm/imx-common/iomux-v3.c b/arch/arm/imx-common/iomux-v3.c
index b59b802..6e46ea8 100644
--- a/arch/arm/imx-common/iomux-v3.c
+++ b/arch/arm/imx-common/iomux-v3.c
@@ -30,6 +30,14 @@
 		(pad & MUX_PAD_CTRL_OFS_MASK) >> MUX_PAD_CTRL_OFS_SHIFT;
 	u32 pad_ctrl = (pad & MUX_PAD_CTRL_MASK) >> MUX_PAD_CTRL_SHIFT;
 
+#if defined CONFIG_MX6SL
+	/* Check whether LVE bit needs to be set */
+	if (pad_ctrl & PAD_CTL_LVE) {
+		pad_ctrl &= ~PAD_CTL_LVE;
+		pad_ctrl |= PAD_CTL_LVE_BIT;
+	}
+#endif
+
 	if (mux_ctrl_ofs)
 		__raw_writel(mux_mode, base + mux_ctrl_ofs);