sh: clkfwk: Convert to IS_ERR_OR_NULL.

Trivial cleanup.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
diff --git a/drivers/sh/clk/core.c b/drivers/sh/clk/core.c
index ebeaa9e..229ad09 100644
--- a/drivers/sh/clk/core.c
+++ b/drivers/sh/clk/core.c
@@ -396,7 +396,7 @@
 {
 	int ret;
 
-	if (clk == NULL || IS_ERR(clk))
+	if (IS_ERR_OR_NULL(clk))
 		return -EINVAL;
 
 	/*