power: supply: add wireless type

Currently, power_supply framework supports only Battery, UPS,
Mains and USB power_supply_type. Add wireless power_supply_type
so that the drivers which supports wireless can register a power
supply class device with POWER_SUPPLY_TYPE_WIRELESS.

Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>
Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>