Input: imx_sc_key - only take the valid data from SCU firmware as key state

When reading key state from SCU, the response data from SCU firmware
is 4 bytes due to MU message protocol, but ONLY the first byte is the
key state, other 3 bytes could be some dirty data, so we should ONLY
take the first byte as key state to avoid reporting incorrect state.
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Fixes: 688f1dfb ("Input: keyboard - imx_sc: Add i.MX system controller key support")
Link: https://lore.kernel.org/r/1576202909-1661-1-git-send-email-Anson.Huang@nxp.comSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/keyboard/imx_sc_key.c

@@ -78,7 +78,13 @@ static void imx_sc_check_for_events(struct work_struct *work)
 		return;
 	}
 
-	state = (bool)msg.state;
+	/*
+	 * The response data from SCU firmware is 4 bytes,
+	 * but ONLY the first byte is the key state, other
+	 * 3 bytes could be some dirty data, so we should
+	 * ONLY take the first byte as key state.
+	 */
+	state = (bool)(msg.state & 0xff);
 
 	if (state ^ priv->keystate) {
 		priv->keystate = state;