Since we added clk enable_count and prograte clk child enabling
operation to clk parent, so add a new function sandbox_clk_enable_count
to get enable_count for test usage.

And add test code to get the enable_count after we enable/disable
the device clk.
Signed-off-by: NPeng Fan <peng.fan@nxp.com>

Add composite clk to sandbox driver
Signed-off-by: NPeng Fan <peng.fan@nxp.com>

This patch provides code to implement the CCF clock tree in sandbox. It
uses all the introduced primitives; some generic ones are reused, some
sandbox specific were developed.

In that way (after introducing the real CCF tree in sandbox) the recently
added to clk-uclass.c: clk_get_by_id() and clk_get_parent_rate() are tested
in their natural work environment.

Usage (sandbox_defconfig and sandbox_flattree_defconfig):
./u-boot --fdt arch/sandbox/dts/test.dtb --command "ut dm clk_ccf"
Signed-off-by: NLukasz Majewski <lukma@denx.de>