libpayload: strings.h: Use builtin __ffs instead of included one

Change-Id: Ie4d0b1b19ce6524341449df8bfabc66bff7bd97e
Signed-off-by: Thomas Heijligen <src@posteo.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/70118
Reviewed-by: Julius Werner <jwerner@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>

payloads/libpayload/include/strings.h

@@ -29,8 +29,6 @@
 #ifndef _STRINGS_H
 #define _STRINGS_H
 
-#include <libpayload.h>
-
-static inline int ffs(int i) { return __ffs(i) + 1; }
+#define ffs(x) __builtin_ffs(x)
 
 #endif