clk: simplify clk_fetch_parent_index() function

The clk_core_get_parent_by_index can be used as a helper function
to simplify the implementation of clk_fetch_parent_index().

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Vladimir Zapolskiy <vz@mleia.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>

drivers/clk/clk.c

@@ -1069,24 +1069,10 @@ static int clk_fetch_parent_index(struct clk_core *core,
 	if (!parent)
 		return -EINVAL;
 
-	/*
-	 * find index of new parent clock using cached parent ptrs,
-	 * or if not yet cached, use string name comparison and cache
-	 * them now to avoid future calls to clk_core_lookup.
-	 */
-	for (i = 0; i < core->num_parents; i++) {
-		if (core->parents[i] == parent)
+	for (i = 0; i < core->num_parents; i++)
+		if (clk_core_get_parent_by_index(core, i) == parent)
 			return i;
 
-		if (core->parents[i])
-			continue;
-
-		if (!strcmp(core->parent_names[i], parent->name)) {
-			core->parents[i] = clk_core_lookup(parent->name);
-			return i;
-		}
-	}
-
 	return -EINVAL;
 }