[PATCH] clk: provide public clk_is_enabled function

[andrew@lunn.ch (Andrew Lunn)]

> Andrew has mentioned, that some bootloaders might disable clocks but
> leave the nodes enabled. Reading those registers would lock up
> the HW, of course. So we thought about to check clk gate status first,
> which this patch is about.
> 
> Of course, we can do clk_enable, read, clk_disable as said before - and
> given the amount of questions and misinterpretation, I think it is the
> saner way.

Hi Sebastian

I agree. As you say, too many people have asked questions or
misinterpretation what is happening, so lets go for the simpler method
people can understand.

I would also suggest in the ethernet driver, maybe set_params(), check
if we have a valid MAC address, and if not, issue a warning and call
to eth_hw_addr_random(dev) to get a random one.

   Andrew