arm64: dts: imx8mq-librem5-devkit: Drop power-supply

It's not a valid binding. Instead move the sdio_rst line to the power
sequence and use w_disable1 as the vmmc-supply bringing it more in line
with other SDIO M2 cards.

Resolves following warning:

arch/arm64/boot/dts/freescale/imx8mq-librem5-devkit.dtb: mmc@30b50000: Unevaluated properties are not allowed ('power-supply' was unexpected)
        from schema $id: http://devicetree.org/schemas/mmc/fsl-imx-esdhc.yaml#



Reported-by: David Heidelberg <david@ixit.cz>
Signed-off-by: Guido Günther <agx@sigxcpu.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>