RDMA/ocrdma: remove unused discard_cnt variable

clang with W=1 reports
drivers/infiniband/hw/ocrdma/ocrdma_verbs.c:1592:6: error: variable
  'discard_cnt' set but not used [-Werror,-Wunused-but-set-variable]
        int discard_cnt = 0;
            ^
This variable is not used so remove it.

Signed-off-by: Tom Rix <trix@redhat.com>
Link: https://lore.kernel.org/r/20230326120959.1351948-1-trix@redhat.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>