HID: Allow HID_BATTERY_STRENGTH to be enabled

Allows for HID_BATTERY_STRENGTH config be enabled without the need for HID
module to be built-in, prior to this HID and POWER_SUPPLY had to be equal, and
now we only select POWER_SUPPLY and depend on the HID module.

Signed-off-by: Daniel Nicoletti <dantti12@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>