init.h: remove long-dead __setup_null_param() macro

This macro appears to have been unused for ages, and there are no
invocations of it anywhere in the source tree.
Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/init.h

@@ -233,9 +233,6 @@ struct obs_kernel_param {
 		__attribute__((aligned((sizeof(long)))))	\
 		= { __setup_str_##unique_id, fn, early }
 
-#define __setup_null_param(str, unique_id)			\
-	__setup_param(str, unique_id, NULL, 0)
-
 #define __setup(str, fn)					\
 	__setup_param(str, fn, fn, 0)
 
@@ -296,7 +293,6 @@ void __init parse_early_param(void);
 	void cleanup_module(void) __attribute__((alias(#exitfn)));
 
 #define __setup_param(str, unique_id, fn)	/* nothing */
-#define __setup_null_param(str, unique_id) 	/* nothing */
 #define __setup(str, func) 			/* nothing */
 #endif