RDMA/ocrdma: Fix compiler warning about int/pointer size mismatch

Fix:

   drivers/infiniband/hw/ocrdma/ocrdma_verbs.c: In function 'ocrdma_build_fr':
>> drivers/infiniband/hw/ocrdma/ocrdma_verbs.c:1832:7: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
     mr = (struct ocrdma_mr *)qp->dev->stag_arr[(hdr->lkey >> 8) &
          ^
   drivers/infiniband/hw/ocrdma/ocrdma_verbs.c: In function 'ocrdma_alloc_frmr':
>> drivers/infiniband/hw/ocrdma/ocrdma_verbs.c:2661:64: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
     dev->stag_arr[(mr->hwmr.lkey >> 8) & (OCRDMA_MAX_STAG - 1)] = (u64) mr;

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>