ext4/001: fix check for zero range support

ext4/001: fix check for zero range support

Ext4/001 fails when run on a file system that does not support byte range
zeroing.  For example, an EOPNOTSUPP failure occurs when the test is run
on a pre-3.15 extent-mapped file system.  The code in the test intended
to prevent this contains an apparent typo that results in a check for
fallocate() rather than zero range support.

Signed-off-by: Eric Whitney <enwlinux@gmail.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>