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

clk_get() return value should be checked with IS_ERR().

Signed-off-by: Aaro Koskinen <[e-mail]>
Acked-by: Kevin Hilman <[e-mail]>
Signed-off-by: Tony Lindgren <[e-mail]>

arch/arm/mach-omap2/io.c

···
 		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);