iputils: really remove patch

It seems the appropiate git rm was missing from 8461038f. Fixes:
http://autobuild.buildroot.net/results/1b1/1b1f63e8c7ba10d4055fb422af6a15c044efc9a6/



Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>