gfs2: remove dead code for quota writes

Since patch 845802b1

 function gfs2_write_buf_to_page checks if the
target inode is jdata or ordered. This function only operates on the
system quota file, which is always jdata, so the check for jdata is
useless. This patch removes it.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>