UPSTREAM: clk: rockchip: validity should be checked prior to cpu clock rate change

UPSTREAM: clk: rockchip: validity should be checked prior to cpu clock rate change

If validity is not checked prior to clock rate change, clk_set_rate(
cpu_clk, unsupported_rate) will return success, but the real clock rate
change operation is prohibited in post clock change event. Alough post
clock change event will report error due to unsupported clock rate is
set, but this error message is ignored by clock framework.

Signed-off-by: Elaine Zhang <zhangqing@rock-chips.com>
Tested-by: Rocky Hao <rocky.hao@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
(am from mmind/linux-rockchip.git branch v4.10-clk/next
 commit a554bb5fb01804a38fde3782831c9567d997939e)

Change-Id: I521700f86fe1d9bf2d1bef4ebe0350cd6f558c0a
Signed-off-by: Jianqun Xu <jay.xu@rock-chips.com>