btrfs: fix range_end calculation in extent_write_locked_range

The range_end field in struct writeback_control is inclusive, just like
the end parameter passed to extent_write_locked_range.  Not doing this
could cause extra writeout, which is harmless but suboptimal.

Fixes: 771ed689 ("Btrfs: Optimize compressed writeback and reads")
CC: stable@vger.kernel.org # 5.9+
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>