Variable 'gen' in reada_for_search() is not used since commit 58dc4ce4
("btrfs: remove unused parameter from readahead_tree_block").  This patch
simply removes this variable.
Signed-off-by: NLuis Henriques <luis.henriques@canonical.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>