route: remove unused sizeof* consts on freebsd

The sizeofSockaddr* consts were replaced by the respective x/sys/unix
consts by CL 632816.

The sizeofIfDataFreeBSD* consts were never used since they were added.

Cq-Include-Trybots: luci.golang.try:x_net-gotip-freebsd-amd64
Change-Id: Ieb0e01353199e08659d45cdc3293e817b679fed5
Reviewed-on: https://go-review.googlesource.com/c/net/+/633155
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Damien Neil <dneil@google.com>
Reviewed-by: Damien Neil <dneil@google.com>

route/defs_freebsd.go

@@ -227,12 +227,6 @@ const (
 	sizeofIfMsghdrFreeBSD10 = C.sizeof_struct_if_msghdr_freebsd10
 	sizeofIfMsghdrFreeBSD11 = C.sizeof_struct_if_msghdr_freebsd11
 
-	sizeofIfDataFreeBSD7  = C.sizeof_struct_if_data_freebsd7
-	sizeofIfDataFreeBSD8  = C.sizeof_struct_if_data_freebsd8
-	sizeofIfDataFreeBSD9  = C.sizeof_struct_if_data_freebsd9
-	sizeofIfDataFreeBSD10 = C.sizeof_struct_if_data_freebsd10
-	sizeofIfDataFreeBSD11 = C.sizeof_struct_if_data_freebsd11
-
 	sizeofRtMsghdrFreeBSD10Emu  = C.sizeof_struct_rt_msghdr
 	sizeofRtMetricsFreeBSD10Emu = C.sizeof_struct_rt_metrics
 
@@ -241,14 +235,4 @@ const (
 	sizeofIfMsghdrFreeBSD9Emu  = C.sizeof_struct_if_msghdr_freebsd9
 	sizeofIfMsghdrFreeBSD10Emu = C.sizeof_struct_if_msghdr_freebsd10
 	sizeofIfMsghdrFreeBSD11Emu = C.sizeof_struct_if_msghdr_freebsd11
-
-	sizeofIfDataFreeBSD7Emu  = C.sizeof_struct_if_data_freebsd7
-	sizeofIfDataFreeBSD8Emu  = C.sizeof_struct_if_data_freebsd8
-	sizeofIfDataFreeBSD9Emu  = C.sizeof_struct_if_data_freebsd9
-	sizeofIfDataFreeBSD10Emu = C.sizeof_struct_if_data_freebsd10
-	sizeofIfDataFreeBSD11Emu = C.sizeof_struct_if_data_freebsd11
-
-	sizeofSockaddrStorage = C.sizeof_struct_sockaddr_storage
-	sizeofSockaddrInet    = C.sizeof_struct_sockaddr_in
-	sizeofSockaddrInet6   = C.sizeof_struct_sockaddr_in6
 )