lwIP: fix some IPv6 errors, eg TCP keepalive

Glue code was inspecting lwIP's netconn "type", checking directly for
NETCONN_UDP and NETCONN_TCP.

Unfortunately the type byte has some flag bits like
"IPv6", which means the tests fail if it's an IPv6 socket. So, for
example, TCP socket options were rejected for IPv6.

Add the necessary NETCONNTYPE_GROUP macros to fix this.

Author: kjbracey

features/FEATURE_LWIP/lwip-interface/lwip_stack.c

@@ -1125,9 +1125,9 @@ static nsapi_error_t mbed_lwip_socket_bind(nsapi_stack_t *stack, nsapi_socket_t
 
     if (
 #if LWIP_TCP
-        (s->conn->type == NETCONN_TCP && s->conn->pcb.tcp->local_port != 0) ||
+        (NETCONNTYPE_GROUP(s->conn->type) == NETCONN_TCP && s->conn->pcb.tcp->local_port != 0) ||
 #endif
-        (s->conn->type == NETCONN_UDP && s->conn->pcb.udp->local_port != 0)) {
+        (NETCONNTYPE_GROUP(s->conn->type) == NETCONN_UDP && s->conn->pcb.udp->local_port != 0)) {
         return NSAPI_ERROR_PARAMETER;
     }
 
@@ -1315,23 +1315,23 @@ static nsapi_error_t mbed_lwip_setsockopt(nsapi_stack_t *stack, nsapi_socket_t h
     switch (optname) {
 #if LWIP_TCP
         case NSAPI_KEEPALIVE:
-            if (optlen != sizeof(int) || s->conn->type != NETCONN_TCP) {
+            if (optlen != sizeof(int) || NETCONNTYPE_GROUP(s->conn->type) != NETCONN_TCP) {
                 return NSAPI_ERROR_UNSUPPORTED;
             }
 
             s->conn->pcb.tcp->so_options |= SOF_KEEPALIVE;
             return 0;
 
         case NSAPI_KEEPIDLE:
-            if (optlen != sizeof(int) || s->conn->type != NETCONN_TCP) {
+            if (optlen != sizeof(int) || NETCONNTYPE_GROUP(s->conn->type) != NETCONN_TCP) {
                 return NSAPI_ERROR_UNSUPPORTED;
             }
 
             s->conn->pcb.tcp->keep_idle = *(int*)optval;
             return 0;
 
         case NSAPI_KEEPINTVL:
-            if (optlen != sizeof(int) || s->conn->type != NETCONN_TCP) {
+            if (optlen != sizeof(int) || NETCONNTYPE_GROUP(s->conn->type) != NETCONN_TCP) {
                 return NSAPI_ERROR_UNSUPPORTED;
             }