Add LoadFirmware() support for NvStorage API

Change-Id: I19f402904978581eb5ca990ffbdf2f762b48c217

BUG=12282
TEST=make H2C firmware and verify using crossystem utility

(set fwb_tries, reboot, verify that mainfw_act is B)

Review URL: http://codereview.chromium.org/6597018
4 files changed