ARM: dts: imx7-colibri: specify usdhc1 supplies

The usdhc1 controller instance is used to provide the default
SD/MMC capabilities of the Colibri standard. The IO pins are
supplied to the SoC on the module whereas the SD-card is powered
by the Carrier Board supply.

Signed-off-by: Stefan Agner <stefan@agner.ch>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>