buildsystem: Drop explicit (k)config.h includes

We have kconfig.h auto-included and it pulls config.h too.

Change-Id: I665a0a168b0d4d3b8f3a27203827b542769988da
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/17655
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins)

src/ec/lenovo/h8/h8.c

@@ -19,7 +19,6 @@
 #include <device/device.h>
 #include <device/pnp.h>
 #include <ec/acpi/ec.h>
-#include <kconfig.h>
 #include <stdlib.h>
 #include <string.h>
 #include <smbios.h>