kconfig: Drop IS_ENABLED() macro

We keep its definition in libpayload, though, to maintain compatibility
with existing payload code. For now.

Change-Id: I8fc0d0136ba2316ef393c5c17f2b3ac3a9c6328d
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/32230
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>

src/include/kconfig.h

@@ -17,7 +17,6 @@
 #define __config_enabled(arg1_or_junk) ___config_enabled(arg1_or_junk 1, 0, 0)
 #define ___config_enabled(__ignored, val, ...) val
 
-#define IS_ENABLED(option) config_enabled(option)	/* deprecated */
 #define CONFIG(option) config_enabled(CONFIG_##option)
 
 #endif