uboot-imx

ARM: dts: am335x-evm: disable mmc3

SDIO is not supported in u-boot, there is no point in enabling mmc3.
For this purpose, add u-boot specific dtsi that this will be included
automatically while building the dtb.

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>