afs: Potential uninitialized variable in afs_extract_data()

Smatch warns that:

    fs/afs/rxrpc.c:922 afs_extract_data()
    error: uninitialized symbol 'remote_abort'.

Smatch is right that "remote_abort" might be uninitialized when we pass
it to afs_set_call_complete().  I don't know if that function uses the
uninitialized variable.  Anyway, the comment for rxrpc_kernel_recv_data(),
says that "*_abort should also be initialised to 0." and this patch does
that.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David Howells <dhowells@redhat.com>