clk: rockchip: Free the memory on the error path

rockchip_clk_register_branch() and rockchip_clk_register_frac_branch()
should free the memory internally when seeing any failure.

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