ARM: dts: dra7-evm: add evm_3v3_sd regulator

Add a node for evm_3v3_sd using onboard pcf GPIO expander which feeds
on to mmc vdd.

Update mapping for vmmc-supply and vmmc_aux-supply.
evm_3v3_sd supplies to SD card vdd, and ldo1 to sdcard i/o lines.

Signed-off-by: Balaji T K <balajitk@ti.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>