clk: Ingenic: Add CGU driver for X1000.

Add support for the clocks provided by the CGU in the Ingenic X1000
SoC, making use of the cgu code to do the heavy lifting.

Signed-off-by: Zhou Yanjie <zhouyanjie@zoho.com>
Link: https://lkml.kernel.org/r/1573378102-72380-3-git-send-email-zhouyanjie@zoho.com
Reviewed-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>