ARM: dts: imx: ventana: GW54xx PMIC swbst reg always-on

The GW54xx PMIC swbst regulator is used for LVDS power, CANbus xceiver
and HDMI DDC and is enabled by the bootloader. Set the regulator to
always-on so that Linux doesn't turn it off thinking its not needed.

Signed-off-by: Tim Harvey <tharvey@gateworks.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>