gfs2: Don't support fallocate on jdata files

We cannot provide an efficient implementation due to the headers
on the data blocks, so there doesn't seem much point in having it.

Signed-off-by: Abhi Das <adas@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>

diff --cc fs/gfs2/file.c
Simple merge