IB/rdamvt: fix cross build with rdmavt

The new check routine causes a larger than supported frame size
on s390.

Changing the check routine to noinline fixes the issue.

Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>