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outdated comments.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/ext4/inode.c b/fs/ext4/inode.c
index 8a43c68..4f7043b 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4894,7 +4894,7 @@
 	offset = inode->i_size & (PAGE_SIZE - 1);
 	/*
 	 * All buffers in the last page remain valid? Then there's nothing to
-	 * do. We do the check mainly to optimize the common PAGE_CACHE_SIZE ==
+	 * do. We do the check mainly to optimize the common PAGE_SIZE ==
 	 * blocksize case
 	 */
 	if (offset > PAGE_SIZE - (1 << inode->i_blkbits))