msm: kgsl: Fix nr_removed calculation while reducing pools

Current code is reducing total_pages by pcount for each
loop iteration which results in decrementing total_pages
incorrectly as pcount is total number of pages reduced
in all previous iterations. Incorrect total_pages results
in incorrect nr_removed. Fix this by not decrementing
total_pages and directly accounting for already reduced
pages in nr_removed calculation.

Change-Id: I69485c26f1f98974eecc30caa1a888ddeafe7c73
Signed-off-by: Deepak Kumar <dkumar@codeaurora.org>