After trimming, set the footprint to the number of pages in use.

A trim can decrease the an mspace footprint but it will not decrease
its max footprint.  We need to decrease the max footprint to make any
pages recovered by a trim available to external allocations.

By setting the ideal footprint after a trim we lift any soft limit in
effect and make the mspace footprint and max footprints equal.

Change-Id: Ia6eb99634ce1d732b417a90291b110d1fc46c2e3