proc/meminfo: update offline region in Memtotal

When memory block is logically offlined, it is still part of System RAM but
is inactive, and can be made active or Onlined anytime.
Take totalram snapshot to include offlined memory in Memtotal.
This method avoids taking device_hotplug lock to meminfo.

Fixes: dc00b6d9 ("proc/meminfo: include offlined region for mem total")
Change-Id: I2b69444e6f066e1c1928278707616840308b00d0
Signed-off-by: Prakash Gupta <guptap@codeaurora.org>