net/socket_rpmsg: add net socket rpmsg support

Change-Id: Ie23ee4c0052cf2fc66972ea9bc5f11c070fbcf8a
Signed-off-by: chao.an <anchao@xiaomi.com>

include/sys/socket.h

@@ -50,6 +50,7 @@
 #define PF_BLUETOOTH  31         /* Bluetooth sockets */
 #define PF_IEEE802154 36         /* Low level IEEE 802.15.4 radio frame interface */
 #define PF_PKTRADIO   64         /* Low level packet radio interface */
+#define PF_RPMSG      65         /* Remote core communication */
 
 /* Supported Address Families. Opengroup.org requires only AF_UNSPEC,
  * AF_UNIX, AF_INET and AF_INET6.
@@ -67,6 +68,7 @@
 #define AF_BLUETOOTH   PF_BLUETOOTH
 #define AF_IEEE802154  PF_IEEE802154
 #define AF_PKTRADIO    PF_PKTRADIO
+#define AF_RPMSG       PF_RPMSG
 
 /* The socket created by socket() has the indicated type, which specifies
  * the communication semantics.