iproute2: drop obsolete patch

libc-compat.h fix for musl was obsolete after 4.16.0 release of iproute2.
Drop it.

Signed-off-by: Maxin John <maxin.john@gmail.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit ad57a1e1)
Signed-off-by: Steve Sakoman <steve@sakoman.com>