msm: msm_iomap: Fix DEBUG_UART for 7x27a/7x30

We have moved to unification of IO address map for 7x27a/7x30 with 8k.
This now means that the header files(msm_iomap-7x30.h and
msm_iomap-7xxx.h) will included whichever target gets compiled,
so now we cannot keep the macro MSM_DEBUG_UART_PHYS in both the
files which has different physical address.
Thus moving to CONFIG_MSM_DEBUG_UART_PHYS which gets selected
from Kconfig based on the target selected.

Change-Id: I024e685d7ce2f5df0db49c482cd5d8541884e054
Signed-off-by: Taniya Das <tdas@codeaurora.org>