ethercatctl: fix hard-coded path to ip utility

- The unmodified upstream iproute2 package installs the ip utility in
  /sbin. That is also where it thus ends up with for example Yocto
  builds.

- Debian/Ubuntu installs it in /bin (and I assume that's how this came
  to be), but their packaging logic provides a symlink /sbin/ip ->
  /bin/ip .

- ArchLinux seems to install it in both places (as hardlinks).

- CentOS only has /sbin/ip.

- Fedora only has /sbin/ip.

So /sbin/ip should work everywhere, whereas /bin/ip does not.

script/ethercatctl.in

@@ -35,7 +35,7 @@ LSMOD=/sbin/lsmod
 MODPROBE=/sbin/modprobe
 RMMOD=/sbin/rmmod
 MODINFO=/sbin/modinfo
-IP=/bin/ip
+IP=/sbin/ip
 
 ETHERCAT=@bindir@/ethercat