count_syscall() always returns 0, optimize it

* defs.h (count_syscall): Change return type from int to void.
* count.c (count_syscall): Change return type from int to void.
* syscall.c (trace_syscall_exiting): Change code around call
to count_syscall accordingly.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
diff --git a/syscall.c b/syscall.c
index 76ef39c..200d8d6 100644
--- a/syscall.c
+++ b/syscall.c
@@ -2419,10 +2419,10 @@
 
 	if (cflag) {
 		struct timeval t = tv;
-		int rc = count_syscall(tcp, &t);
+		count_syscall(tcp, &t);
 		if (cflag == CFLAG_ONLY_STATS) {
 			tcp->flags &= ~TCB_INSYSCALL;
-			return rc;
+			return 0;
 		}
 	}