msm: board-8960: Modify SMPS7 min, max voltage limits for 8960ab

PM8921 SMPS7 is the parent regulator for the LDOs which supply
to the Q6 processors. The worst case voltage for Q6 processor
on 8960ab is 1.075V (compared to 1.05V on 8960). Raise the S7
voltage constraints from 1.15V to 1.275V in order to accommodate
the increase in Q6 supply voltage.

CRs-Fixed: 507062
Change-Id: If3e249b6412d141d7108332b43481e127c350bb2
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>