serial: 8250_exar: Adjust IOT2000 matching

Since there are more IOT2040 variants with identical hardware but
different asset tags, the asset tag matching should be adjusted to
support them.

As only the IOT2040 variants have the Exar chip on board, matching on
their board name is enough. In the future there will be no other devices
with the "SIMATIC IOT2000" DMI board name but different hardware.

Signed-off-by: Su Bao Cheng <[e-mail]>
Reviewed-by: Jan Kiszka <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/serial/8250/8250_exar.c

···
 	.register_gpio = iot2040_register_gpio,
 };
 
+/*
+ * For SIMATIC IOT2000, only IOT2040 and its variants have the Exar device,
+ * IOT2020 doesn't have. Therefore it is sufficient to match on the common
+ * board name after the device was found.
+ */
 static const struct dmi_system_id exar_platforms[] = {
 	{
 		.matches = {
 			DMI_EXACT_MATCH(DMI_BOARD_NAME, "SIMATIC IOT2000"),
-			DMI_EXACT_MATCH(DMI_BOARD_ASSET_TAG,
-					"6ES7647-0AA00-1YA2"),
 		},
 		.driver_data = (void *)&iot2040_platform,
 	},