power: qpnp-fg-gen3: Fine tune the monotonic SOC calculation

Currently, all the values of raw monotonic SOC (0-255) gets
rounded off to 0-100. This can show up monotonic SOC hitting 0%
earlier when the SOC hadn't really hit zero yet. Improve the
SOC round off calculation so that 0 and 100 % can be shown when
it reaches the exact point.

Change-Id: I5bd9ebc8667a5beed9e1e97ff492aa1350f4d0f7
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>