of_batterydata: Add snapshot of of_batterydata library

Add snapshot of of_batterydata library as of msm-4.14
'commit 7e16ff6cdde5 ("defconfig: qcs405: enable WLAN configs for 32-bit
QCS405")'.

Also fix the declaration of of_batterydata_get_best_profile by returning
a NULL pointer instead of an (error) integer.

Change-Id: Ida58f61e86b4aea673b1aba59702a51ae0c0287c
Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>