btrfs: defrag, use unsigned type for extent thresh
btrfs: defrag, use unsigned type for extent thresh

Signed type mismatches the ioctl structure, all extent calculations are
done on unsigned types.

Signed-off-by: David Sterba <a2ce9d316ca04d17b520237d2846a218b8284e52@suse.cz>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs