can: c_can: use proper type for 'instance'

Commit 6439fbce (can: c_can: fix error checking of priv->instance in
probe()) found the warning but applied a suboptimal solution. Since, both
pdev->id and of_alias_get_id() return integers, it makes sense to convert the
variable to an integer and avoid the cast.
Signed-off-by: Wolfram Sang <wsa@sang-engineering.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/c_can/c_can.h

@@ -183,7 +183,7 @@ struct c_can_priv {
 	void *priv;		/* for board-specific data */
 	enum c_can_dev_id type;
 	u32 __iomem *raminit_ctrlreg;
-	unsigned int instance;
+	int instance;
 	void (*raminit) (const struct c_can_priv *priv, bool enable);
 	u32 comm_rcv_high;
 	u32 rxmasked;

drivers/net/can/c_can/c_can_platform.c

@@ -222,7 +222,7 @@ static int c_can_plat_probe(struct platform_device *pdev)
 
 		res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
 		priv->raminit_ctrlreg = devm_ioremap_resource(&pdev->dev, res);
-		if (IS_ERR(priv->raminit_ctrlreg) || (int)priv->instance < 0)
+		if (IS_ERR(priv->raminit_ctrlreg) || priv->instance < 0)
 			dev_info(&pdev->dev, "control memory is not used for raminit\n");
 		else
 			priv->raminit = c_can_hw_raminit;