Input: pcspkr - fix fall-through warnings for Clang

In preparation to enable -Wimplicit-fallthrough for Clang, fix a warning
by explicitly adding a break statement instead of just letting the code
fall through to the next case.

Signed-off-by: Gustavo A. R. Silva <[e-mail]>
Link: https://lore.kernel.org/r/4b[e-mail]
Signed-off-by: Dmitry Torokhov <[e-mail]>

drivers/input/misc/pcspkr.c

···
 	case SND_BELL:
 		if (value)
 			value = 1000;
+		break;
 	case SND_TONE:
 		break;
 	default: