power: vm_bms: use DIV_ROUND_CLOSEST for soc and acc calculation

The kernel does not provide the round off feature for normal div
function. The DIV_ROUND_CLOSEST macro should be used in the soc and
acc calculation for rounding off the data.

Change-Id: I72d5b3ed5f90859b01909677f66c2abb65d4c9ec
Signed-off-by: Jie Cheng <rockiec@codeaurora.org>