internal/socket: add missing import to zos-s390x file

Redo of go.dev/cl/425534, but w/o accidental binary file.

Fixes golang/go#54676

Change-Id: I69de5bd49f8d5be6d263b7eef0f491aba992bdbe
Reviewed-on: https://go-review.googlesource.com/c/net/+/425697
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
diff --git a/internal/socket/sys_zos_s390x.go b/internal/socket/sys_zos_s390x.go
index fc65e62..eaa896c 100644
--- a/internal/socket/sys_zos_s390x.go
+++ b/internal/socket/sys_zos_s390x.go
@@ -5,6 +5,7 @@
 package socket
 
 import (
+	"net"
 	"syscall"
 	"unsafe"
 )