GFS2: Remove obsolete quota tunable

There is no need for a paramater which relates to the internals
of quota to be exposed to users. The only possible use would be
to turn it up so large that the memory allocation fails. So lets
remove it and set it to a sensible value which ensures that we
don't ask for multipage allocations.

Currently the size of struct gfs2_holder means that the caluclated
value is identical to the previous default value, so there should
be no functional change.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Cc: Abhijith Das <adas@redhat.com>