RDMA/erdma: Add the erdma_query_pkey() interface

RDMA/erdma: Add the erdma_query_pkey() interface

The erdma_query_pkey() interface queries the PKey at the specified
index. Currently, erdma supports only one partition and returns the
default PKey for each query. Besides, the correct length of the PKey
table can be obtained by calling the erdma_query_port() and
erdma_get_port_immutable() interfaces.

Signed-off-by: Boshi Yu <boshiyu@linux.alibaba.com>
Link: https://patch.msgid.link/20241211020930.68833-4-boshiyu@linux.alibaba.com
Reviewed-by: Cheng Xu <chengyou@linux.alibaba.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>