RDMA/core: create struct ib_port_cache

As Jason suggested, we have 4 elements for per port arrays,
it's better to have a separate structure to represent them.

It simplifies code a bit, ~ 30 lines of code less :)
Signed-off-by: Jack Wang <jinpu.wang@profitbricks.com>
Reviewed-by: Michael Wang <yun.wang@profitbricks.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

include/rdma/ib_verbs.h

@@ -1775,13 +1775,17 @@ enum ib_mad_result {
 
 #define IB_DEVICE_NAME_MAX 64
 
+struct ib_port_cache {
+	struct ib_pkey_cache  *pkey;
+	struct ib_gid_table   *gid;
+	u8                     lmc;
+	enum ib_port_state     port_state;
+};
+
 struct ib_cache {
 	rwlock_t                lock;
 	struct ib_event_handler event_handler;
-	struct ib_pkey_cache  **pkey_cache;
-	struct ib_gid_table   **gid_cache;
-	u8                     *lmc_cache;
-	enum ib_port_state     *port_state_cache;
+	struct ib_port_cache   *ports;
 };
 
 struct ib_dma_mapping_ops {