svcrdma: Remove last two __GFP_NOFAIL call sites

Clean up.

These functions can otherwise fail, so check for page allocation
failures too.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Acked-by: Bruce Fields <bfields@fieldses.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>