Revert "route: remove unused sizeof* consts on freebsd"

This reverts CL 633155.

Reason for revert: This is part of a short chain of CLs that causes
x/net to depend on x/sys. We have a policy that prevents us from
vendoring x/sys into std, but x/net needs to be vendored.

Change-Id: Ib773f21dee59fe6f4afb7ba1d7ae01d8859110c6
Reviewed-on: https://go-review.googlesource.com/c/net/+/634255
Auto-Submit: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
diff --git a/route/zsys_freebsd_amd64.go b/route/zsys_freebsd_amd64.go
index d563b86..2f6cf35 100644
--- a/route/zsys_freebsd_amd64.go
+++ b/route/zsys_freebsd_amd64.go
@@ -13,6 +13,12 @@
 	sizeofIfMsghdrFreeBSD10 = 0xa8
 	sizeofIfMsghdrFreeBSD11 = 0xa8
 
+	sizeofIfDataFreeBSD7  = 0x98
+	sizeofIfDataFreeBSD8  = 0x98
+	sizeofIfDataFreeBSD9  = 0x98
+	sizeofIfDataFreeBSD10 = 0x98
+	sizeofIfDataFreeBSD11 = 0x98
+
 	sizeofRtMsghdrFreeBSD10Emu  = 0x98
 	sizeofRtMetricsFreeBSD10Emu = 0x70
 
@@ -21,4 +27,14 @@
 	sizeofIfMsghdrFreeBSD9Emu  = 0xa8
 	sizeofIfMsghdrFreeBSD10Emu = 0xa8
 	sizeofIfMsghdrFreeBSD11Emu = 0xa8
+
+	sizeofIfDataFreeBSD7Emu  = 0x98
+	sizeofIfDataFreeBSD8Emu  = 0x98
+	sizeofIfDataFreeBSD9Emu  = 0x98
+	sizeofIfDataFreeBSD10Emu = 0x98
+	sizeofIfDataFreeBSD11Emu = 0x98
+
+	sizeofSockaddrStorage = 0x80
+	sizeofSockaddrInet    = 0x10
+	sizeofSockaddrInet6   = 0x1c
 )