ARM: dts: msm: Add label for PMIC5

In driver code, some register offsets are different for PMIC5. Add
label to identify PMIC5 to select correct register offsets.

Change-Id: I5a1aa6101f7ef27b2b77398dc03296cf0ec0336c
Signed-off-by: Jishnu Prakash <jprakash@codeaurora.org>