spi/sh-hspi: fix return value check in hspi_probe().

According to its documentation, clk_get() returns a "valid IS_ERR() condition
containing errno", so we should call IS_ERR() rather than a NULL check.
Signed-off-by: Cyril Roelandt <tipecaml@gmail.com>
Acked-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

drivers/spi/spi-sh-hspi.c

@@ -290,7 +290,7 @@ static int hspi_probe(struct platform_device *pdev)
 	}
 
 	clk = clk_get(NULL, "shyway_clk");
-	if (!clk) {
+	if (IS_ERR(clk)) {
 		dev_err(&pdev->dev, "shyway_clk is required\n");
 		ret = -EINVAL;
 		goto error0;