2760_battery: export more features

Export POWER_SUPPLY_PROP_TIME_TO_EMPTY_NOW and POWER_SUPPLY_PROP_CAPACITY
features to the power supply core.

Signed-off-by: Daniel Mack <daniel@caiaq.de>
Cc: Szabolcs Gyurko <szabolcs.gyurko@tlt.hu>
Acked-by: Matt Reimer <mreimer@vpop.net>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>