ARM: dts: msm: use PM8150 LDO 18 for USB SS supply on SM8150 QRD DVT boards

The VDDA_USB1_SS_DP_CORE supply has been changed from PM8150
LDO 5 to LDO 18 on SM8150 QRD DVT boards.  Override the USB SS
vdd-supply property with the new mapping.

Also, increase the voltage for this supply from 880 mV to 912 mV
to improve USB performance.

Change-Id: I7b54c422ef1e95ba497034a4b277658bebaacf87
Signed-off-by: David Collins <collinsd@codeaurora.org>