i2c: rcar: fix clk_get() error handling

When clk_get() fails, it returns an error code, not a NULL. This patch
fixes such an error handling bug.
Signed-off-by: NGuennadi Liakhovetski <g.liakhovetski+renesas@gmail.com>
Signed-off-by: NWolfram Sang <wsa@the-dreams.de>

drivers/i2c/busses/i2c-rcar.c

@@ -234,9 +234,9 @@ static int rcar_i2c_clock_calculate(struct rcar_i2c_priv *priv,
 	u32 cdf_width;
 	unsigned long rate;
 
-	if (!clkp) {
-		dev_err(dev, "there is no peripheral_clk\n");
-		return -EIO;
+	if (IS_ERR(clkp)) {
+		dev_err(dev, "couldn't get clock\n");
+		return PTR_ERR(clkp);
 	}
 
 	switch (priv->devtype) {