busybox:udhcpc: Remove the routes from the right interface

When using iproute2 to remove the route all default rules
will be removed. Scope the removal by interface like it is
done with ifconfig.

(From OE-Core rev: 2127a57cb1b3d83f9f7640051403e47e485b132c)

Signed-off-by: Holger Hans Peter Freyther <holger@moiji-mobile.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-core/busybox/files/simple.script

@@ -46,7 +46,7 @@ case "$1" in
 		if [ -n "$router" ] ; then
 			if ! root_is_nfs ; then
                                 if [ $have_bin_ip -eq 1 ]; then
-                                        while ip route del default 2>/dev/null ; do
+                                        while ip route del default dev $interface 2>/dev/null ; do
                                                 :
                                         done
                                 else