powercap: RAPL: Fix a NULL vs IS_ERR() bug

The devm_ioremap_resource() function returns error pointers on error,
it never returns NULL.  Update the check accordingly.

Fixes: 9eef7f9d ("powercap: intel_rapl: Introduce RAPL TPMI interface driver")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Acked-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/powercap/intel_rapl_tpmi.c

@@ -255,8 +255,8 @@ static int intel_rapl_tpmi_probe(struct auxiliary_device *auxdev,
 	}
 
 	trp->base = devm_ioremap_resource(&auxdev->dev, res);
-	if (!trp->base) {
-		ret = -ENOMEM;
+	if (IS_ERR(trp->base)) {
+		ret = PTR_ERR(trp->base);
 		goto err;
 	}