clk: intel: Add CGU clock driver for a new SoC

clk: intel: Add CGU clock driver for a new SoC

Clock Generation Unit(CGU) is a new clock controller IP of a forthcoming
Intel network processor SoC named Lightning Mountain(LGM). It provides
programming interfaces to control & configure all CPU & peripheral clocks.
Add common clock framework based clock controller driver for CGU.

Signed-off-by: Rahul Tanwar <rahul.tanwar@linux.intel.com>
Link: https://lkml.kernel.org/r/42a4f71847714df482bacffdcd84341a4052800b.1587102634.git.rahul.tanwar@linux.intel.com
[sboyd@kernel.org: Kill init function to alloc and cleanup newline]
Signed-off-by: Stephen Boyd <sboyd@kernel.org>