clk: rockchip: convert rk3399 pll type to use readl_relaxed_poll_timeout

Instead of open coding the polling of the lock status, use the handy
readl_relaxed_poll_timeout for this. As the pll locking is normally
blazingly fast and we don't want to incur additional delays, we're
not doing any sleeps similar to for example the imx clk-pllv4
and define a very safe but still short timeout of 1ms.

Suggested-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Heiko Stuebner <heiko.stuebner@theobroma-systems.com>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20200129163821.1547295-1-heiko@sntech.de