power: qpnp-vm-bms: report end-of-charging based on last_soc

Previous design used calculated_soc to report EOC(end of charging),
while soc based resume charging based on last_soc. If calculated_soc
toggles occasionally, charging state and SOC(state of charge) will
be in a mess.

Fix this kind of issue by reporting end-of-charging based on last_soc.

CRs-Fixed: 655107
Change-Id: Ia06b58eb00bc82c95ff42b3347f07af76cb538d5
Signed-off-by: Zhenhua Huang <zhenhuah@codeaurora.org>