[Buildroot] [PATCH 1/2] iproute2: fix build with threads support disabled

[Petr Vorel]

> iproute2 renamed the configure script generated file to config.mk.
> Update the berkeleydb disable code.

> Fixes:
> http://autobuild.buildroot.net/results/46d/46da1142806fb524326994585cec6de9f7f3f480/
> http://autobuild.buildroot.net/results/3aa/3aa028fe9e730335d2af00d5969b674a3d9f640b/

> Cc: Petr Vorel <petr.vorel at gmail.com>
> Signed-off-by: Baruch Siach <baruch at tkos.co.il>
> ---
Acked-by: Petr Vorel <petr.vorel at gmail.com>