ARM: dts: msm: Update modem size for BG targets

Re-factor and update memory carveout configuration for
BlackGhost apq and msm targets into separate file and
include it directly. Increase modem firmware region by
2MB for these targets.

Change-Id: I0421e6e0fd2c9580f8cf8f769287b6afafa81b2a
Signed-off-by: Shiraz Hashim <shashim@codeaurora.org>