msm: charger: Add msm_charger

MSM 8660 FFA has two charging paths one via an SMPS charger chip isl9519q
and other via the pmic 8058 chip's linear charger.
Write a driver which talks to the power supply framework and also decides
the optimal charging path depending on the charging cable presence and
battery capacity.

Change-Id: Id00ba526651cb8da688b48b4d1e1d1eb178c1e87
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>