internal/socket: add structure definitions for linux/ppc

Add the generated structure definitions for linux/ppc.  This file was
created using gccgo 10.2.1 and the command:

    GOARCH=ppc CC=powerpc-linux-gnu-gcc go tool cgo -godefs defs_linux.go

Fixes golang/go#45677

internal/socket/zsys_linux_ppc.go

@@ -0,0 +1,35 @@
+// Code generated by cmd/cgo -godefs; DO NOT EDIT.
+// cgo -godefs defs_linux.go
+
+package socket
+
+type iovec struct {
+	Base	*byte
+	Len	uint32
+}
+
+type msghdr struct {
+	Name		*byte
+	Namelen		uint32
+	Iov		*iovec
+	Iovlen		uint32
+	Control		*byte
+	Controllen	uint32
+	Flags		int32
+}
+
+type mmsghdr struct {
+	Hdr	msghdr
+	Len	uint32
+}
+
+type cmsghdr struct {
+	Len	uint32
+	Level	int32
+	Type	int32
+}
+
+const (
+	sizeofIovec	= 0x8
+	sizeofMsghdr	= 0x1c
+)