ARM: OMAP2+: PM: fix return value check in omap2_set_init_voltage()

In case of error, the function voltdm_lookup() returns NULL
not ERR_PTR(). The IS_ERR() test in the return value check
should be replaced with NULL test.

dpatch engine is used to auto generate this patch.
(https://github.com/weiyj/dpatch)
Signed-off-by: NWei Yongjun <yongjun_wei@trendmicro.com.cn>
Acked-by: NJean Pihet <j-pihet@ti.com>
Signed-off-by: NKevin Hilman <khilman@ti.com>

arch/arm/mach-omap2/pm.c

@@ -176,7 +176,7 @@ static int __init omap2_set_init_voltage(char *vdd_name, char *clk_name,
 	}
 
 	voltdm = voltdm_lookup(vdd_name);
-	if (IS_ERR(voltdm)) {
+	if (!voltdm) {
 		pr_err("%s: unable to get vdd pointer for vdd_%s\n",
 			__func__, vdd_name);
 		goto exit;