ARM: dts: msm: Correct the halt base offsets for modem on msm8996

Load and use the mss_q6, mss_modem and mss_nc register addresses
from DT instead of relying on the common offsets.

Change-Id: I0457e678bd0cc096edc5f032693d0d2790b3d175
Signed-off-by: Deepak Katragadda <dkatraga@codeaurora.org>