AFS: checking wrong bit in afs_readpages()

We should be testing "if (vnode->flags & (1 << 4))" instead of
"if (vnode->flags & 4) {".  The current test checks if the data was
modified instead of deleted.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>