ARM: dts: msm: Specify NOMINAL bus vote for sdmmagpie

DWC3 driver exposes a sysfs node to let user change
its bus vote to a lower or min value. Currently there
are three entries in the DT for sdmmagpie. But in order
to support MIN and NOMINAL bus votes it should be aligned
with driver. Driver expects DT entries for bus votes as:

NONE
NOMINAL
SVS
MIN
MAX

This change specifies NOMINAL bus vote to align with
dwc3 driver.

Change-Id: I4148638be4c110d4720732416f71be3583a938f3
Signed-off-by: Pratham Pratap <prathampratap@codeaurora.org>