Input: mark expected switch fall-throughs

In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.

Warning level 2 was used: -Wimplicit-fallthrough=2

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
diff --git a/drivers/input/mouse/sermouse.c b/drivers/input/mouse/sermouse.c
index d27816a..3e8fb81 100644
--- a/drivers/input/mouse/sermouse.c
+++ b/drivers/input/mouse/sermouse.c
@@ -139,7 +139,8 @@ static void sermouse_process_ms(struct sermouse *sermouse, signed char data)
 			switch (sermouse->type) {
 
 				case SERIO_MS:
-					 sermouse->type = SERIO_MP;
+					sermouse->type = SERIO_MP;
+					/* fall through */
 
 				case SERIO_MP:
 					if ((data >> 2) & 3) break;	/* M++ Wireless Extension packet. */
@@ -150,6 +151,7 @@ static void sermouse_process_ms(struct sermouse *sermouse, signed char data)
 				case SERIO_MZP:
 				case SERIO_MZPP:
 					input_report_key(dev, BTN_SIDE,   (data >> 5) & 1);
+					/* fall through */
 
 				case SERIO_MZ:
 					input_report_key(dev, BTN_MIDDLE, (data >> 4) & 1);