pmdomain: core: Fix error checking in genpd_dev_pm_attach_by_id()

The error checking for of_count_phandle_with_args() does not handle
negative error codes correctly.  The problem is that "index" is a u32 so
in the condition "if (index >= num_domains)" negative error codes stored
in "num_domains" are type promoted to very high positive values and
"index" is always going to be valid.

Test for negative error codes first and then test if "index" is valid.

Fixes: 3ccf3f0 ("PM / Domains: Enable genpd_dev_pm_attach_by_id|name() for single PM domain")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/aBxPQ8AI8N5v-7rL@stanley.mountain
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Author: Dan Carpenter

drivers/pmdomain/core.c

@@ -3126,7 +3126,7 @@ struct device *genpd_dev_pm_attach_by_id(struct device *dev,
 	/* Verify that the index is within a valid range. */
 	num_domains = of_count_phandle_with_args(dev->of_node, "power-domains",
 						 "#power-domain-cells");
-	if (index >= num_domains)
+	if (num_domains < 0 || index >= num_domains)
 		return NULL;
 
 	/* Allocate and register device on the genpd bus. */