RDMA/ocrdma: Make ocrdma_pma_counters() return void

This function always returns 0, so just use void and remove the bogus
checking at the only call site.

Link: https://lore.kernel.org/r/20191029062745.7932-6-leon@kernel.org


Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>