ARM: dts: msm: add proxy consumers for L6C and L9C regulators on Lahaina

Add proxy consumer configurations for the SD card supply regulators
PM8350C LDO 6 and 9 which ensure that these regulators will be
automatically disabled in the case that bootloaders enable the
regulators and HLOS APPS consumers make no requests for them.

Also increase the L6C initial voltage to 2.96 V as this is a safe
functional default voltage.

Change-Id: I7d5cc58fe34307ac68b790b742144ec47153ad0b