coreboot: Replace all IS_ENABLED(CONFIG_XXX) with CONFIG(XXX)

This patch is a raw application of

 find src/ -type f | xargs sed -i -e 's/IS_ENABLED\s*(CONFIG_/CONFIG(/g'

Change-Id: I6262d6d5c23cabe23c242b4f38d446b74fe16b88
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/31774
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

src/cpu/intel/hyperthreading/intel_sibling.c

@@ -19,7 +19,7 @@
 #include <smp/spinlock.h>
 #include <assert.h>
 
-#if IS_ENABLED(CONFIG_PARALLEL_CPU_INIT)
+#if CONFIG(PARALLEL_CPU_INIT)
 #error Intel hyper-threading requires serialized CPU init
 #endif