xfs/176: fix broken setup code

xfs/176: fix broken setup code

The test does not pass the mkfs output through the mkfs filter, so
the inode size is not set up correctly. Hence it calculates the
CHUNK_SIZE as 0, and it ends up getting stuck in an endless loop
throwing ENOSPC errors because the offset never changes.

While there, use 'echo -n' rather than 'touch' to create zero length
files much faster.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Zorro lang <zlang@redhat.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>