clk: rockchip: disable alt_parent clk in err cases when registering cpuclk

Add clk_disable_unprepare to handle cpuclk->alt_parent if
rockchip_clk_register_cpuclk fails.

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>