xfs_repair: check the ftype of dot and dotdot directory entries

xfs_repair: check the ftype of dot and dotdot directory entries

The long-format directory block checking code skips the filetype check
for the '.' and '..' entries, even though they're part of the ondisk
format.  This leads to repair failing to catch subtle corruption at the
start of a directory.

Found by fuzzing bu[0].filetype = zeroes in xfs/386.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>