clk: Add Ingenic JZ4755 CGU driver

Add support for the clocks provided by the CGU in the Ingenic JZ4755
SoC.

Signed-off-by: Siarhei Volkau <lis8215@gmail.com>
Link: https://lore.kernel.org/r/20221031183930.1338009-2-lis8215@gmail.com
Signed-off-by: Stephen Boyd <sboyd@kernel.org>