xfs: scrub: Remove incorrect check executed on block format directories

A directory with one directory block which in turns consists of two or more fs
blocks is incorrectly flagged as corrupt by scrub since it assumes that
"Block" format directories have a data fork single extent spanning the file
offset range of [0, Dir block size - 1].

This commit fixes the bug by removing the incorrect check.

Signed-off-by: Chandan Babu R <chandanrlinux@gmail.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>