arm64: dts: imx8mq-librem5: Fix gpio-hog property

arm64: dts: imx8mq-librem5: Fix gpio-hog property

The 'lane-mapping' property is not a valid one and cause the following
schema warning:

imx8mq-librem5-r2.dtb: pmic-5v-hog: 'lane-mapping' does not match any of the regexes: 'pinctrl-[0-9]+'
	from schema $id: http://devicetree.org/schemas/gpio/gpio-hog.yaml#

Replace it with 'line-name'.

Signed-off-by: Fabio Estevam <festevam@denx.de>
Reviewed-by: Guido Günther <agx@sigxcpu.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>