power: qpnp-bms: Fix 100% SoC reporting

In some MSMs including 8974, there is no more heartbeat work updating
userspace with power supply updates. This can result in a strange
situation where the battery is full, but reported SoC is still 99%
because userspace is only updated when calculated SoC is changed. If
calculated SoC is unchanged at 100%, reported SoC will not change
either.

Fix this by always calling report_state_of_charge when calculating
SoC. Also, invalidate last soc when transitioning from charging to
full in order to allow BMS to report 100%.

Change-Id: Ib1697c3370c19901ef468c0db5665d265e1e7598
Signed-off-by: Xiaozhe Shi <xiaozhes@codeaurora.org>