msm: memory: Add memblock_reserve bindings to dt reserve code

Drivers may wish to just reserve a block of memory in addition to
removing it or adding a size to a general pool. Update the DT
scanning code to scan for these bindings and reserve the memory.

Change-Id: Ic55c4271670a655f26a11d47a0d64cc525f9bfb2
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>