This libc header has sockaddr definition in user space.

Fixes user space compilation errors like these from kernel headers including
only linux/socket.h:

error: field ‘ifru_addr’ has incomplete type
struct sockaddr ifru_addr;
error: field ‘_sockaddr’ has incomplete type
struct sockaddr  _sockaddr;
error: invalid application of ‘sizeof’ to incomplete type ‘struct sockaddr’

With this following uapi headers now compile in user space:

rdma/rdma_user_rxe.h
linux/vm_sockets.h
linux/ncp_fs.h
linux/nfc.h
linux/phonet.h

Signed-off-by: Mikko Rapeli <redacted>
Cc: netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Cc: Dmitry V. Levin <ldv-u2l5PoMzF/Vg9hUCZPvPmw@public.gmane.org>
---
 include/uapi/linux/socket.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/uapi/linux/socket.h b/include/uapi/linux/socket.h
index 76ab0c68561e..8a81197cc08b 100644
--- a/include/uapi/linux/socket.h
+++ b/include/uapi/linux/socket.h

@@ -1,6 +1,10 @@
 #ifndef _UAPI_LINUX_SOCKET_H
 #define _UAPI_LINUX_SOCKET_H
 
+#ifndef __KERNEL__
+#include <sys/socket.h>
+#endif