unix: add socket constants

Fixes golang/go#53557

Change-Id: Ic3d57d9431d7c89f6650ff742888481bcabb23c6
Reviewed-on: https://go-review.googlesource.com/c/sys/+/417994
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

unix/mkerrors.sh

@@ -297,6 +297,10 @@ struct ltchars {
 #define SOL_NETLINK	270
 #endif
 
+#ifndef SOL_SMC
+#define SOL_SMC 286
+#endif
+
 #ifdef SOL_BLUETOOTH
 // SPARC includes this in /usr/include/sparc64-linux-gnu/bits/socket.h
 // but it is already in bluetooth_linux.go

unix/zerrors_linux.go

@@ -2940,6 +2940,7 @@ const (
 	SOL_RAW                                     = 0xff
 	SOL_RDS                                     = 0x114
 	SOL_RXRPC                                   = 0x110
+	SOL_SMC                                     = 0x11e
 	SOL_TCP                                     = 0x6
 	SOL_TIPC                                    = 0x10f
 	SOL_TLS                                     = 0x11a