clk: abstract parent cache

Abstract access to the clock parent cache by defining
clk_get_parent_by_index(clk, index). This allows access to parent
clocks from clock drivers.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Cc: Mike Turquette <mturquette@linaro.org>
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Mike Turquette <mturquette@linaro.org>
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 9487b96..a834092 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -420,6 +420,7 @@
 struct clk_hw *__clk_get_hw(struct clk *clk);
 u8 __clk_get_num_parents(struct clk *clk);
 struct clk *__clk_get_parent(struct clk *clk);
+struct clk *clk_get_parent_by_index(struct clk *clk, u8 index);
 unsigned int __clk_get_enable_count(struct clk *clk);
 unsigned int __clk_get_prepare_count(struct clk *clk);
 unsigned long __clk_get_rate(struct clk *clk);