ARM: dts: dra7-evm: add pinmux configuration for mmc1/2

Add pinmux configuration for SD card slot and eMMC device
found on TI's DRA74x EVM.

Only the default modes are supported. For higher speed modes
(UHS and HS200) to function, we need full fledged IODelay support
in kernel. IODelay support is yet to be added.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
[nsekhar@ti.com: rebase to mainline/master, use IOPAD() macro,
		 update commit message]
Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>