ssb: chipcommon: fix fall-through annotation

Replace "Fallthough" with a proper "fall through" annotation.

This fix is part of the ongoing efforts to enabling
-Wimplicit-fallthrough

Signed-off-by: Gustavo A. R. Silva <[e-mail]>
Acked-by: Michael Buesch <[e-mail]>
Signed-off-by: Kalle Valo <[e-mail]>

drivers/ssb/driver_chipcommon.c

···
 			*m = chipco_read32(cc, SSB_CHIPCO_CLOCK_M2);
 			break;
 		}
-		/* Fallthough */
+		/* Fall through */
 	default:
 		*m = chipco_read32(cc, SSB_CHIPCO_CLOCK_SB);
 	}