ARM: dts: imx6sl-evk: Keep VGEN1 regulator always enabled

On imx6sl-evk board the VGEN1 regulator powers up the NVCC_1P2V domain of the
imx6sl SoC, so we need to keep it always powered.

According to imx6sl datasheet the GPIO block has three supplies:
NVCC33_IO, NVCC18_IO and NVCC_1P2V and it states that:
"All digital I/O supplies (NVCC_xxxx) must be powered under normal conditions
whether the associated I/O pins are in use or not"

This problem has been observed by the fact that a GPIO connected to an LED could
not work when the PMIC driver was enabled.

Keeping VGEN1 regulator always enabled fixes the problem.
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

arch/arm/boot/dts/imx6sl-evk.dts

@@ -195,6 +195,7 @@ vref_reg: vrefddr {
 			vgen1_reg: vgen1 {
 				regulator-min-microvolt = <800000>;
 				regulator-max-microvolt = <1550000>;
+				regulator-always-on;
 			};
 
 			vgen2_reg: vgen2 {