arm64: dts: imx8mq: Add the buck vdd_arm regulator

According to the schematics, this is a MP2147 switch converter
which is controlled by GPIO1_IO13. When set the gpio is set to
high the regulator output is set to 0.9V. When the gpio is set
to low the regulator output is set to 1V.

Signed-off-by: Abel Vesa <abel.vesa@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>