power_supply: Add BATT_PROFILE_VERSION property

Add POWER_SUPPLY_PROP_BATT_PROFILE_VERSION to report
the version of the battery profile used by Qgauge.

Change-Id: I857c59ba2c4a9b2648f7aa708d6feba7295dd3cc
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>