generic/235: work with 64k block size

With 64k blocksized filesystem, this test fails since a single 8k write
will actually end up consuming 64k. Hence this commit writes 64k data
into the test file.

Signed-off-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
Tested-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>
2 files changed