clk: rockchip: convert rk3036 pll type to use internal lock status

The rk3036 pll type exposes its lock status in both its pllcon registers
as well as the General Register Files. To remove one dependency convert
it to the "internal" lock status, similar to how rk3399 handles it.

Signed-off-by: Heiko Stuebner <heiko.stuebner@theobroma-systems.com>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20200129163821.1547295-3-heiko@sntech.de