arm: omap2: io: fix clk_get() error check

clk_get() return value should be checked with IS_ERR().
Signed-off-by: Aaro Koskinen <aaro.koskinen@nokia.com>
Acked-by: Kevin Hilman <khilman@deeprootsystems.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/mach-omap2/io.c

@@ -297,7 +297,7 @@ static int __init _omap2_init_reprogram_sdrc(void)
 		return 0;
 
 	dpll3_m2_ck = clk_get(NULL, "dpll3_m2_ck");
-	if (!dpll3_m2_ck)
+	if (IS_ERR(dpll3_m2_ck))
 		return -EINVAL;
 
 	rate = clk_get_rate(dpll3_m2_ck);