pvrdma: check return value from pvrdma_idx_ring_has_ routines

pvrdma: check return value from pvrdma_idx_ring_has_ routines

pvrdma_idx_ring_has_[data/space] routines also return invalid
index PVRDMA_INVALID_IDX[=-1], if ring has no data/space. Check
return value from these routines to avoid plausible infinite loops.

Reported-by: Li Qiang <liq3ea@163.com>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
Reviewed-by: Yuval Shaia <yuval.shaia@oracle.com>
Signed-off-by: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
(cherry picked from commit f1e2e38ee0136b7710a2caa347049818afd57a1b)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>