smb347-charger: Fix battery status reporting logic for charger faults

This patch checks for charger status register for determining the
battery charging status and reports Discharing/Charging/Not Charging/Full
accordingly.

This patch also adds the interrupt support for Safety Timer Expiration.
This interrupt is helpful in debugging the cause for charger fault.

Signed-off-by: Ramakrishna Pallala <ramakrishna.pallala@intel.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>