mfd: si476x-i2c: Fix spelling mistake in case() statement's FALLTHROUGH comment

's/FALLTHROUG/FALLTHROUGH'

Cc: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/si476x-i2c.c

@@ -588,7 +588,7 @@ static int si476x_core_fwver_to_revision(struct si476x_core *core,
 			goto unknown_revision;
 		}
 	case SI476X_FUNC_BOOTLOADER:
-	default:		/* FALLTHROUG */
+	default:		/* FALLTHROUGH */
 		BUG();
 		return -1;
 	}