msm: kgsl: Populate a valid pointer to page as vmf->page

The array of pages can have a valid pointer to page when checked under
the memdesc spinlock, but as soon as the lock is released, it can
become null in an attempt to reclaim the page. It is to be noted that
only the pointer in the array of pages became null and the actual page
would still be valid, as refcount on the page is incremented within the
lock which would fail the attempt to reclaim. So make sure that a valid
pointer to page is assigned to vmf->page. Also, avoid unnecessary
setting of the skip reclaim flag.

Change-Id: Iffde9d7a76ef4f46a1421bec226c1a828b05c63f
Signed-off-by: Puranam V G Tejaswi <pvgtejas@codeaurora.org>