This fixes pmu_init() failing on pit, where the charger task isn't
enabled yet (and thus the charger interrupt is NULL - which can't be
enabled).
BUG=chrome-os-partner:18657
BRANCH=none
TEST=build all platforms; on pit, check that pmu_init() no longer fails
Change-Id: I191bbaeb4df10241e3508ccf7ef5ea83f42c5697
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/49550
Reviewed-by: Simon Glass <sjg@chromium.org>