ARM: omap2+: hwmod: fix potential NULL pointer access

omap_hwmod_get_pwrdm() may access a NULL clk_hw pointer in some failure
cases. Add a check for the case and bail out gracely if this happens.
Reported-by: Dan Murphy <dmurphy@ti.com>
Signed-off-by: Tero Kristo <t-kristo@ti.com>
Cc: stable@vger.kernel.org # v5.10+
Signed-off-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/mach-omap2/omap_hwmod.c

@@ -3776,6 +3776,7 @@ struct powerdomain *omap_hwmod_get_pwrdm(struct omap_hwmod *oh)
 	struct omap_hwmod_ocp_if *oi;
 	struct clockdomain *clkdm;
 	struct clk_hw_omap *clk;
+	struct clk_hw *hw;
 
 	if (!oh)
 		return NULL;
@@ -3792,7 +3793,14 @@ struct powerdomain *omap_hwmod_get_pwrdm(struct omap_hwmod *oh)
 		c = oi->_clk;
 	}
 
-	clk = to_clk_hw_omap(__clk_get_hw(c));
+	hw = __clk_get_hw(c);
+	if (!hw)
+		return NULL;
+
+	clk = to_clk_hw_omap(hw);
+	if (!clk)
+		return NULL;
+
 	clkdm = clk->clkdm;
 	if (!clkdm)
 		return NULL;