selftests: timestamping: Fix SIOCGSTAMP undeclared build failure

Add missing linux/sockios.h include to fix the following SIOCGSTAMP
undeclared build error. In addition, remove the local defines for
SIOCGSTAMPNS and SIOCSHWTSTAMP and pick them up from linux/sockios.h.

timestamping.c:249:19: error: SIOCGSTAMP undeclared
   if (ioctl(sock, SIOCGSTAMP, &tv))
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

tools/testing/selftests/networking/timestamping/timestamping.c

@@ -32,6 +32,7 @@
 #include <asm/types.h>
 #include <linux/net_tstamp.h>
 #include <linux/errqueue.h>
+#include <linux/sockios.h>
 
 #ifndef SO_TIMESTAMPING
 # define SO_TIMESTAMPING         37
@@ -42,14 +43,6 @@
 # define SO_TIMESTAMPNS 35
 #endif
 
-#ifndef SIOCGSTAMPNS
-# define SIOCGSTAMPNS 0x8907
-#endif
-
-#ifndef SIOCSHWTSTAMP
-# define SIOCSHWTSTAMP 0x89b0
-#endif
-
 static void usage(const char *error)
 {
 	if (error)