util/cbmem: Workaround for IS_ENABLED()

Our include files reference CONFIG_xxx declarations, which we should
ignore for utility build.

We cannot include kconfig.h to get IS_ENABLED() as that file
would require build/config.h and we do not want to enforce a build
of the firmware to be able to build the utility.

Since we do not include build/config.h each occurence of CONFIG_xxx
in the included header files is undefined and will be treated as
disabled.

Change-Id: I74f1627fc3f294410db8ce486ab553dac9e967f4
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/6066
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>

util/cbmem/cbmem.c

@@ -36,6 +36,7 @@
 
 #define ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]))
 #define MAP_BYTES (1024*1024)
+#define IS_ENABLED(x) (defined (x) && (x))
 
 #include "boot/coreboot_tables.h"