msm: improve handling of DONT_MAP_HOLE_AFTER_MEMBANK0

The code to avoid mapping the hole after memory bank 0
located the start and size of this hole after running
generic initialization code which needed to convert
physical addresses to virtual ones and vice-versa
beyond this hole.

While this didn't prevent the kernel from booting, this
isn't clean, and in fact it was giving us more vmalloc
space than the config file specified (and as a result
there was less lowmem than expected).

The code to locate the hole now runs before this
initialization code.

Change-Id: Id67d8b9ea489b6d6a2c20151b0fc9a9d7b5b662d
Signed-off-by: Larry Bassel <lbassel@codeaurora.org>