thermal: gov_fair_share: Eliminate unnecessary integer divisions

The computations carried out by fair_share_throttle() for each trip
point include at least one redundant integer division which introduces
superfluous rounding errors.  Also the multiplications by 100 in it are
not really necessary and can be eliminated.

Rearrange fair_share_throttle() to carry out only one integer division per
trip and only as many integer multiplications as necessary and rename one
variable in it (while at it).

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>