sh: clkfwk: Handle clk_get_sys() returning an ERR_PTR.

clk_get() needs to also perform an IS_ERR() check to see whether
clk_get_sys() failed or not.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

arch/sh/kernel/cpu/clock.c

@@ -399,7 +399,7 @@ struct clk *clk_get(struct device *dev, const char *id)
 	int idno;
 
 	clk = clk_get_sys(dev_id, id);
-	if (clk)
+	if (clk && !IS_ERR(clk))
 		return clk;
 
 	if (dev == NULL || dev->bus != &platform_bus_type)