AFS: Guard afs_file_readpage_read_complete() definition with CONFIG_AFS_FSCACHE

If CONFIG_AFS_FSCACHE is not defined, the following warning is displayed when
fs/afs/file.c is compiled:

 fs/afs/file.c:111: warning: ‘afs_file_readpage_read_complete’ defined but not used

This occurs because all calls to this function are guarded by
CONFIG_AFS_FSCACHE.  Thus, guard its definition as well.
Signed-off-by: Matt Kraai <kraai@ftbfs.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/afs/file.c

@@ -102,6 +102,7 @@ int afs_release(struct inode *inode, struct file *file)
 	return 0;
 }
 
+#ifdef CONFIG_AFS_FSCACHE
 /*
  * deal with notification that a page was read from the cache
  */
@@ -117,6 +118,7 @@ static void afs_file_readpage_read_complete(struct page *page,
 		SetPageUptodate(page);
 	unlock_page(page);
 }
+#endif
 
 /*
  * AFS read page from file, directory or symlink