drivers: power: Reorganize batterydata-lib.c

Move batterydata-lib.c to drivers/power/* and remove
the dependency from arch/arm/mach-msm/*.

While at it remove the CONFIG_PM8921_BMS entry from
the arch/arm/mach-msm/Makefile as it is not supported
anymore.

Change-Id: Ie9f548198c0614e8489b137c4ac8b906b7e0dffb
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>