msm: kgsl: improve memory stats maintenance

While freeing memory, page_alloc memstat wrongly shows
that the memory is freed while the process is still ongoing.
While allocating memory if something goes wrong during the
process, the memory allocated till that point is not
reflected in page_alloc. Change the point of updation of
page_alloc. Also add two stats, one to track allocation in
progress and the other to track free in progress.

Change-Id: I494c873fd90b8e504d5eea6966855b50493d9c09
Signed-off-by: Puranam V G Tejaswi <pvgtejas@codeaurora.org>