route: avoid unnecessary type conversions

CL generated mechanically with github.com/mdempsky/unconvert.

Change-Id: I22eea0b991462dd00f3fa28073a8b886e19bc068
Reviewed-on: https://go-review.googlesource.com/100095
Run-TryBot: Kunpei Sakai <namusyaka@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alberto Donizetti <alb.donizetti@gmail.com>

route/syscall.go

@@ -20,7 +20,7 @@ func sysctl(mib []int32, old *byte, oldlen *uintptr, new *byte, newlen uintptr)
 	} else {
 		p = unsafe.Pointer(&zero)
 	}
-	_, _, errno := syscall.Syscall6(syscall.SYS___SYSCTL, uintptr(p), uintptr(len(mib)), uintptr(unsafe.Pointer(old)), uintptr(unsafe.Pointer(oldlen)), uintptr(unsafe.Pointer(new)), uintptr(newlen))
+	_, _, errno := syscall.Syscall6(syscall.SYS___SYSCTL, uintptr(p), uintptr(len(mib)), uintptr(unsafe.Pointer(old)), uintptr(unsafe.Pointer(oldlen)), uintptr(unsafe.Pointer(new)), newlen)
 	if errno != 0 {
 		return error(errno)
 	}