ARM: dts: imx6sx-sdb: Assign corresponding power supply for LDOs

ARM: dts: imx6sx-sdb: Assign corresponding power supply for LDOs

On i.MX6SX SDB board, vgen6 supplies vdd1p1/vdd2p5 LDO and
sw2 supplies vdd3p0 LDO, this patch assigns corresponding power
supply for vdd1p1/vdd2p5/vdd3p0 to avoid confusion by below log:

vdd1p1: supplied by regulator-dummy
vdd3p0: supplied by regulator-dummy
vdd2p5: supplied by regulator-dummy

With this patch, the power supply is more accurate:

vdd1p1: supplied by VGEN6
vdd3p0: supplied by SW2
vdd2p5: supplied by VGEN6

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>