clk: fixed-rate: Document accuracy member

This member isn't documented, leading to kernel-doc warnings. Document
it.

Cc: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lkml.kernel.org/r/20190830150923.259497-6-sboyd@kernel.org

include/linux/clk-provider.h

@@ -321,6 +321,7 @@ struct clk_hw {
  * struct clk_fixed_rate - fixed-rate clock
  * @hw:		handle between common and hardware-specific interfaces
  * @fixed_rate:	constant frequency of clock
+ * @fixed_accuracy: constant accuracy of clock in ppb (parts per billion)
  */
 struct clk_fixed_rate {
 	struct		clk_hw hw;