clk: rockchip: Remove unused/undocumented struct members from clk-cpu

clk: rockchip: Remove unused/undocumented struct members from clk-cpu

Fixes the following W=1 kernel build warning(s):

 drivers/clk/rockchip/clk-cpu.c:65: warning: Function parameter or member 'cpu_mux' not described in 'rockchip_cpuclk'
 drivers/clk/rockchip/clk-cpu.c:65: warning: Function parameter or member 'cpu_mux_ops' not described in 'rockchip_cpuclk'

Cc: Michael Turquette <mturquette@baylibre.com>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: Heiko Stuebner <heiko@sntech.de>
Cc: Thomas Abraham <thomas.ab@samsung.com>
Cc: linux-clk@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-rockchip@lists.infradead.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20210120093040.1719407-3-lee.jones@linaro.org
Signed-off-by: Heiko Stuebner <heiko@sntech.de>