proc: remove now unneeded ADDBUF macro

After local seq_file conversion it was forgotten.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>

fs/proc/array.c

@@ -86,11 +86,6 @@
 #include <asm/processor.h>
 #include "internal.h"
 
-/* Gcc optimizes away "strlen(x)" for constant x */
-#define ADDBUF(buffer, string) \
-do { memcpy(buffer, string, strlen(string)); \
-     buffer += strlen(string); } while (0)
-
 static inline void task_name(struct seq_file *m, struct task_struct *p)
 {
 	int i;