ftrace: build fix

fix:

 In file included from init/main.c:65:
 include/linux/ftrace.h:166: error: expected ‘,' or ‘;' before ‘{' token
 make[1]: *** [init/main.o] Error 1
 make: *** [init/main.o] Error 2

Signed-off-by: Ingo Molnar <mingo@elte.hu>