OPP: Fix potential null ptr dereference in dev_pm_opp_get_required_pstate()

"opp" pointer is dereferenced before the IS_ERR_OR_NULL() check. Fix it by
removing the dereference to cache opp_table and dereference it directly
where opp_table is used.

This fixes the following smatch warning:

drivers/opp/core.c:232 dev_pm_opp_get_required_pstate() warn: variable
dereferenced before IS_ERR check 'opp' (see line 230)

Fixes: 84cb7ff ("OPP: pstate is only valid for genpd OPP tables")
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

Author: Mani-Sadhasivam

drivers/opp/core.c

@@ -226,20 +226,18 @@ EXPORT_SYMBOL_GPL(dev_pm_opp_get_level);
 unsigned int dev_pm_opp_get_required_pstate(struct dev_pm_opp *opp,
 					    unsigned int index)
 {
-	struct opp_table *opp_table = opp->opp_table;
-
 	if (IS_ERR_OR_NULL(opp) || !opp->available ||
-	    index >= opp_table->required_opp_count) {
+	    index >= opp->opp_table->required_opp_count) {
 		pr_err("%s: Invalid parameters\n", __func__);
 		return 0;
 	}
 
 	/* required-opps not fully initialized yet */
-	if (lazy_linking_pending(opp_table))
+	if (lazy_linking_pending(opp->opp_table))
 		return 0;
 
 	/* The required OPP table must belong to a genpd */
-	if (unlikely(!opp_table->required_opp_tables[index]->is_genpd)) {
+	if (unlikely(!opp->opp_table->required_opp_tables[index]->is_genpd)) {
 		pr_err("%s: Performance state is only valid for genpds.\n", __func__);
 		return 0;
 	}