target: msm8952: Improve shutdown detect function

In bear targets if KEYPAD_PWR key pressed for very
short time before PS_HOLD goes high, means if
KEYPAD_PWR released before MSM resets, it will
come as PON1 trigger in Pmic, LK boots up to kernel
and sends pause for battery charging in kernel which
is wrong, so added battery connected check in LK
and decision taken accordingly.

Change-Id: Iadd629469ae1d6825dec4b7573ef4a68e67c2d34