Make internal APIs static, and remove board_ prefix for clarity.
Move TSU6721 calls from charger task to extpower_usb functions for
better encapsulation.
No functional changes, just moving code. Yes, this will make
cherry-picking back from spring to TOT less convenient, but now the
code is more readable and it will make maintaining the PMU code easier
as we add boards.
BUG=chrome-os-partner:18343
BRANCH=none
TEST=build spring
Change-Id: I52b37e57fc8519859996a110b0503277c6f0bbc8
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/47657