[NET]: Adding SO_TIMESTAMPNS / SCM_TIMESTAMPNS support

Now that network timestamps use ktime_t infrastructure, we can add a new
SOL_SOCKET sockopt  SO_TIMESTAMPNS.

This command is similar to SO_TIMESTAMP, but permits transmission of
a 'timespec struct' instead of a 'timeval struct' control message.
(nanosecond resolution instead of microsecond)

Control message is labelled SCM_TIMESTAMPNS instead of SCM_TIMESTAMP

A socket cannot mix SO_TIMESTAMP and SO_TIMESTAMPNS : the two modes are
mutually exclusive.

sock_recv_timestamp() became too big to be fully inlined so I added a
__sock_recv_timestamp() helper function.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
CC: linux-arch@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/asm-sh/socket.h b/include/asm-sh/socket.h
index ca70362..c48d6fc 100644
--- a/include/asm-sh/socket.h
+++ b/include/asm-sh/socket.h
@@ -49,5 +49,7 @@
 
 #define SO_PEERSEC		31
 #define SO_PASSSEC		34
+#define SO_TIMESTAMPNS		35
+#define SCM_TIMESTAMPNS		SO_TIMESTAMPNS
 
 #endif /* __ASM_SH_SOCKET_H */