afs: Fix afs_store_data() to set mtime in new operation descriptor

Fix afs_store_data() so that it sets the mtime in the new operation
descriptor otherwise the mtime on the server gets set to 0 when a write is
stored to the server.

Fixes: e49c7b2f ("afs: Build an abstraction around an "operation" concept")
Reported-by: NDave Botsch <botsch@cnf.cornell.edu>
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fs/afs/write.c

@@ -447,6 +447,7 @@ static int afs_store_data(struct address_space *mapping,
 	op->store.last = last;
 	op->store.first_offset = offset;
 	op->store.last_to = to;
+	op->mtime = vnode->vfs_inode.i_mtime;
 	op->ops = &afs_store_data_operation;
 
 try_next_key: