msm: Update meminfo to reflect consecutive memory holes

The device tree now has a node for each of the memory regions
belonging to the subsystems. The meminfo blocks are updated to
reflect these memory holes in such a way that every meminfo block
is of a non-zero size. The start and end of the largest memory
hole is calculated using the meminfo.

Change-Id: I9eb9984f9d74cf2a493846cb2ae7f83db9f92719
Signed-off-by: Neeti Desai <neetid@codeaurora.org>