x86: replace hardcoded number

Replace "4" in time_32.c code by sizeof(long).
This way, it can work on x86_64 too.
Signed-off-by: Glauber Costa <gcosta@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/time_32.c

@@ -49,7 +49,7 @@ unsigned long profile_pc(struct pt_regs *regs)
 #ifdef CONFIG_SMP
 	if (!user_mode_vm(regs) && in_lock_functions(pc)) {
 #ifdef CONFIG_FRAME_POINTER
-		return *(unsigned long *)(regs->bp + 4);
+		return *(unsigned long *)(regs->bp + sizeof(long));
 #else
 		unsigned long *sp = (unsigned long *)&regs->sp;