power: smb-lib: Add support to detect weak charger

A weak charger might trigger switcher_power_ok interrupt storm
which gets incorrectly detected as a boost_back condition and
input gets suspended. Add a logic to distinguish a weak charger
and the boost_back condition by first reducing the ICL current
to a lower value (500mA by default) on detecting a
switcher_power_ok storm. If the switcher_ok storm disappears
then its indeed a weak charger and if the storm continues its
possibly a boost_back condition.

Change-Id: I46b406e403aa16a502e6da149b180545848fc906
Signed-off-by: Ashay Jaiswal <ashayj@codeaurora.org>