mm, fs: remove remaining PAGE_CACHE_* and page_cache_{get,release} usage

Mostly direct substitution with occasional adjustment or removing
outdated comments.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c
index 1a9c664..446753d 100644
--- a/fs/ubifs/file.c
+++ b/fs/ubifs/file.c
@@ -554,7 +554,7 @@
 		 * VFS copied less data to the page that it intended and
 		 * declared in its '->write_begin()' call via the @len
 		 * argument. If the page was not up-to-date, and @len was
-		 * @PAGE_CACHE_SIZE, the 'ubifs_write_begin()' function did
+		 * @PAGE_SIZE, the 'ubifs_write_begin()' function did
 		 * not load it from the media (for optimization reasons). This
 		 * means that part of the page contains garbage. So read the
 		 * page now.