HID: input: Fix fall-through warnings for Clang

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

Link: https://github.com/KSPP/linux/issues/115
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-input.c

@@ -746,6 +746,7 @@ static void hidinput_configure_usage(struct hid_input *hidinput, struct hid_fiel
 				field->flags |= HID_MAIN_ITEM_RELATIVE;
 				break;
 			}
+			goto unknown;
 
 		default: goto unknown;
 		}