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/arch/arm/armv7/mmu.c

@@ -29,7 +29,6 @@
  */
 
 #include <assert.h>
-#include <config.h>
 #include <stdlib.h>
 #include <stdint.h>
 #include <symbols.h>

src/arch/arm/include/armv4/arch/cache.h

@@ -32,7 +32,6 @@
 #ifndef ARM_CACHE_H
 #define ARM_CACHE_H
 
-#include <config.h>
 #include <stddef.h>
 #include <stdint.h>
 

src/arch/arm64/include/armv8/arch/cache.h

@@ -32,7 +32,6 @@
 #ifndef ARM_ARM64_CACHE_H
 #define ARM_ARM64_CACHE_H
 
-#include <config.h>
 #include <stddef.h>
 #include <stdint.h>
 #include <arch/barrier.h>