net: socket: replace calls to sys_send() with __sys_sendto()

sys_send() merely expands the parameters to __sys_sendto() by NULL and 0.
Open-code this in the two places which used sys_send() as a wrapper to
__sys_sendto().

This patch is part of a series which removes in-kernel calls to syscalls.
On this basis, the syscall entry path can be streamlined. For details, see
http://lkml.kernel.org/r/20180325162527.GA17492@light.dominikbrodowski.net

Cc: David S. Miller <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>

net/compat.c

@@ -837,7 +837,7 @@ COMPAT_SYSCALL_DEFINE2(socketcall, int, call, u32 __user *, args)
 		ret = __sys_socketpair(a0, a1, a[2], compat_ptr(a[3]));
 		break;
 	case SYS_SEND:
-		ret = sys_send(a0, compat_ptr(a1), a[2], a[3]);
+		ret = __sys_sendto(a0, compat_ptr(a1), a[2], a[3], NULL, 0);
 		break;
 	case SYS_SENDTO:
 		ret = __sys_sendto(a0, compat_ptr(a1), a[2], a[3],

net/socket.c

@@ -2558,7 +2558,8 @@ SYSCALL_DEFINE2(socketcall, int, call, unsigned long __user *, args)
 		err = __sys_socketpair(a0, a1, a[2], (int __user *)a[3]);
 		break;
 	case SYS_SEND:
-		err = sys_send(a0, (void __user *)a1, a[2], a[3]);
+		err = __sys_sendto(a0, (void __user *)a1, a[2], a[3],
+				   NULL, 0);
 		break;
 	case SYS_SENDTO:
 		err = __sys_sendto(a0, (void __user *)a1, a[2], a[3],