btrfs: use pagevec_lookup_range_tag()

btrfs: use pagevec_lookup_range_tag()

We want only pages from given range in btree_write_cache_pages() and
extent_write_cache_pages().  Use pagevec_lookup_range_tag() instead of
pagevec_lookup_tag() and remove unnecessary code.

Link: http://lkml.kernel.org/r/20171009151359.31984-3-jack@suse.cz
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: David Sterba <dsterba@suse.com>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: David Sterba <dsterba@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>