spi: s3c64xx: avoid possible negative array index

The platform id is used as an index into the fifo_lvl_mask array.
Platforms can come with a negative device ID, PLATFORM_DEVID_NONE (-1),
thus we risked a negative array index. Catch such cases and fail to
probe.
Reviewed-by: Sam Protsenko <semen.protsenko@linaro.org>
Reviewed-by: Peter Griffin <peter.griffin@linaro.org>
Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Link: https://lore.kernel.org/r/20240207120431.2766269-6-tudor.ambarus@linaro.orgSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-s3c64xx.c

@@ -1189,6 +1189,9 @@ static int s3c64xx_spi_probe(struct platform_device *pdev)
 					     "Failed to get alias id\n");
 		sdd->port_id = ret;
 	} else {
+		if (pdev->id < 0)
+			return dev_err_probe(&pdev->dev, -EINVAL,
+					     "Negative platform ID is not allowed\n");
 		sdd->port_id = pdev->id;
 	}