Btrfs: fix that check_int_data mount option was ignored

The bitfield member mount_opt was too small by one bit to hold the mount
option that enabled to include data extents in the integrity checker.
Since the same issue happened when the BTRFS_MOUNT_PANIC_ON_FATAL_ERROR
option was added (git rebase silently merges so that the increase of the
size of the bitfield member is lost), the bit limit was removed entirely.

Signed-off-by: Stefan Behrens <sbehrens@giantdisaster.de>