writeback: Export inode_io_list_del()

Ext4 needs to remove inode from writeback lists after it is out of
visibility of its journalling machinery (which can still dirty the
inode). Export inode_io_list_del() for it.

Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20200421085445.5731-3-jack@suse.cz


Signed-off-by: Theodore Ts'o <tytso@mit.edu>