power: Add battery driver for goldfish emulator

Add the emulated power driver for the Goldfish platform.

This folds together the code from the Google tree, Jun Nakajima's cleanups
and x86 porting work, and then a tidy up to pass checkpatch.

Signed-off-by: Mike A. Chan <mikechan@google.com>
[cleanup and x86 support]
Signed-off-by: Sheng Yang <sheng@linux.intel.com>
Signed-off-by: Yunhong Jiang <yunhong.jiang@intel.com>
Signed-off-by: Xiaohui Xin <xiaohui.xin@intel.com>
Signed-off-by: Jun Nakajima <jun.nakajima@intel.com>
Signed-off-by: Bruce Beare <bruce.j.beare@intel.com>
[ported to 3.4]
Signed-off-by: Tom Keel <thomas.keel@intel.com>
[ported to 3.7 and final tidy]
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Anton Vorontsov <anton@enomsg.org>