ARM: dts: imx7d-smegw01: Remove unneeded #address-cells/#size-cells

Remove the unneeded #address-cells/#size-cells from sram@0 to fix
the following 'make CHECK_DTBS=y imx7d-smegw01.dtb' warning:

sram@0: Unevaluated properties are not allowed ('#address-cells', '#size-cells' were unexpected)
From schema: Documentation/devicetree/bindings/mtd/microchip,mchp48l640.yaml

Signed-off-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>