clk: ingenic: Use readl_poll_timeout instead of custom loop

Use the readl_poll_timeout() function instead of rolling our own
busy-wait loops. This makes the code simpler.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Link: https://lore.kernel.org/r/20200903015048.3091523-2-paul@crapouillou.net


Signed-off-by: Stephen Boyd <sboyd@kernel.org>