nfsd: use fsnotify_data_inode() to get the unlinked inode

The inode argument to handle_event() is about to become obsolete.

Link: https://lore.kernel.org/r/20200708111156.24659-4-amir73il@gmail.com


Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>