clk: Document and simplify clk_core_get_rate_nolock()

This function uses a few gotos and doesn't explain why parents and
numbers of parents are being checked before returning different values
for the clk's rate. Document and simplify this function somewhat to make
this better.
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

drivers/clk/clk.c

@@ -345,23 +345,18 @@ unsigned int __clk_get_enable_count(struct clk *clk)
 
 static unsigned long clk_core_get_rate_nolock(struct clk_core *core)
 {
-	unsigned long ret;
-
-	if (!core) {
-		ret = 0;
-		goto out;
-	}
-
-	ret = core->rate;
-
-	if (!core->num_parents)
-		goto out;
+	if (!core)
+		return 0;
 
-	if (!core->parent)
-		ret = 0;
+	if (!core->num_parents || core->parent)
+		return core->rate;
 
-out:
-	return ret;
+	/*
+	 * Clk must have a parent because num_parents > 0 but the parent isn't
+	 * known yet. Best to return 0 as the rate of this clk until we can
+	 * properly recalc the rate based on the parent's rate.
+	 */
+	return 0;
 }
 
 unsigned long clk_hw_get_rate(const struct clk_hw *hw)