ANDROID: mm: Add vendor hook in filemap_get_folio()

Add a vendor hook for pagecache hit/miss and other
vendor specific functions.

Bug: 174088128
Bug: 172987241
Signed-off-by: Chiawei Wang <chiaweiwang@google.com>
Change-Id: Ie9f14a69a86b8ed81de766e44e30f2eba1d9bd84
Signed-off-by: Richard Chang <richardycc@google.com>
(cherry picked from commit db158b4a)
Signed-off-by: Jack Lee <liangjlee@google.com>