ring-buffer: Use fallthrough pseudo-keyword

Replace /* fall through */ comment with pseudo-keyword macro fallthrough[1]

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through

Link: https://lkml.kernel.org/r/20210511140246.18868-1-jj251510319013@gmail.comSigned-off-by: Wei Ming Chen <jj251510319013@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/ring_buffer.c

@@ -3391,7 +3391,7 @@ static void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
 		case RINGBUF_TYPE_PADDING:
 			if (event->time_delta == 1)
 				break;
-			/* fall through */
+			fallthrough;
 		case RINGBUF_TYPE_DATA:
 			ts += event->time_delta;
 			break;