clk: initial common clk support ...

This adds barebox common clk support loosely based on the Kernel common
clk support. differences are:

- barebox does not need prepare/unprepare
- no parent rate propagation for set_rate
- struct clk is not really encapsulated from the drivers

Along with the clk support we have support for some basic clk building
blocks:

- clk-fixed
- clk-fixed-factor
- clk-mux
- clk-divider

clk-fixed and clk-fixed-factor are completely generic, clk-mux and clk-divider
are currently the way i.MX muxes/dividers are implemented.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

clk clkdev: Add clkdev matching based on physbase ...

Most clock/device associations can be done based on the physical
base address of the corresponding device. So instead of depending
on string matching add an optional possibility to associate a clock
lookups with physical addresses. This also has the advantage that
the lookups for devicetree based devices can be identical to the
platform based devices.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

arm: move clkdev to drivers/clk ...

as refer in this patch "arm & sh: factorised duplicated clkdev.c"

factorise some generic infrastructure to assist looking up struct clks
for the ARM & SH architecture.

as the code is identical at 99% in linux

move it also as preparing for the SH adding

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>