clk: ti: autoidle: add checks against NULL pointer reference

The clk pointer passed to omap2_clk_(deny|allow)_idle can be NULL, so
add checks for this.

Reported-by: Dan Murphy <dmurphy@ti.com>
Signed-off-by: Tero Kristo <t-kristo@ti.com>

drivers/clk/ti/autoidle.c

@@ -47,6 +47,9 @@ int omap2_clk_deny_idle(struct clk *clk)
 {
 	struct clk_hw_omap *c;
 
+	if (!clk)
+		return -EINVAL;
+
 	c = to_clk_hw_omap(__clk_get_hw(clk));
 	if (c->ops && c->ops->deny_idle)
 		c->ops->deny_idle(c);
@@ -63,6 +66,9 @@ int omap2_clk_allow_idle(struct clk *clk)
 {
 	struct clk_hw_omap *c;
 
+	if (!clk)
+		return -EINVAL;
+
 	c = to_clk_hw_omap(__clk_get_hw(clk));
 	if (c->ops && c->ops->allow_idle)
 		c->ops->allow_idle(c);