zlog: Add patch to remove -Werror

Add patch to remove -Werror and avoid build errors because of warnings.

Fixes: http://autobuild.buildroot.net/results/6935e1107d832e5678c8742239eccd89d4abed47/


Signed-off-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>