btrfs: raid56: fix memory leak of btrfs_raid_bio::stripe_uptodate_bitmap

btrfs: raid56: fix memory leak of btrfs_raid_bio::stripe_uptodate_bitmap

We allocate the bitmap but we never free it in free_raid_bio_pointers().
Fix this by adding a bitmap_free() call against the stripe_uptodate_bitmap
of a raid bio.

Fixes: 1810350b04ef ("btrfs: raid56: move sector_ptr::uptodate into a dedicated bitmap")
Reported-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/linux-btrfs/20260126045315.GA31641@lst.de/
Reviewed-by: Qu Wenruo <wqu@suse.com>
Tested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>