power_supply: Convert drivers/power/* to use module_platform_driver()

This patch converts the drivers in drivers/power/* to use the
module_platform_driver() macro which makes the code smaller and a bit
simpler.

Cc: Mike Rapoport <mike@compulab.co.il>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Nithish Mahalingam <nithish.mahalingam@intel.com>
Cc: MyungJoo Ham <myungjoo.ham@samsung.com>
Cc: Haojian Zhuang <haojian.zhuang@marvell.com>
Cc: Balaji Rao <balajirrao@openmoko.org>
Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Clifton Barnes <cabarnes@indesign-llc.com>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>