RDMA/ocrdma: populate max_sge_rd in device attributes

max_sge_rd is used by some of the ULPs to calculate the maximum
number of SGEs that can be used for RDMA READ. Populating this
value in the response of query_device verb. Also, avoid checking
the max_srq_sge while populating max_sge.

Signed-off-by: Selvin Xavier <selvin.xavier@broadcom.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>