Correct the formula of battery capacity estimation.

Instead of
  (current charge) * (current battery level percentage)
the formula should be
  (current charge) / (current battery level percentage)
to estimate the charge at 100% battery level.

Bug: 34255953
Fixes: 34255953
Test: formula change CL. No existing unit tests found.
Change-Id: I56ef7af3fb097a3082e0ef24329f522d2a0229cc