power: Support non-INT power signal pins
power: Support non-INT power signal pins

Optionally do polling for power signal pins
which are not set as INT pins.

BUG=b:64528567
BRANCH=none
TEST=boot scarlet rev1 with a non-INT power signal pin

Change-Id: I327753fcc0f1c6482c5f5eb3df28f67181b4eb62
Signed-off-by: Philip Chen <3ee404f9ef892bc3fda6e6a76e65843b5fa44db2@google.com>
Reviewed-on: https://chromium-review.googlesource.com/611649
Commit-Ready: Philip Chen <3ee404f9ef892bc3fda6e6a76e65843b5fa44db2@chromium.org>
Tested-by: Philip Chen <3ee404f9ef892bc3fda6e6a76e65843b5fa44db2@chromium.org>
Reviewed-by: Randall Spangler <62698fdbb84d1779579ee80c3f39fac22017e5bc@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec