msm: arch_add_memory should only perform logical memory hotplug

The function arch_add_memory() should only perform logical
memory hotplug, but it was also improperly performing
physical memory hotplug. Even worse, it was adding pages
to the free list before the memory bank they were in
was powered on.

Signed-off-by: Larry Bassel <lbassel@codeaurora.org>
(cherry picked from commit 61fe47257aa9fa598163dda4a3938090bf7d95c6)