clk: Add Ingenic jz4770 CGU driver

Add support for the clocks provided by the CGU in the Ingenic JZ4770
SoC.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Maarten ter Huurne <maarten@treewalker.org>
Acked-by: Stephen Boyd <sboyd@codeaurora.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/18482/


Signed-off-by: James Hogan <jhogan@kernel.org>