[PATCH v3] pwm: add CSR SiRFSoC PWM driver

[Barry Song]

>
> i think what we can make everything clear is making the channel clocks
> become clock nodes of the whole clock tree, the node can be requested
> by a non-PWM device and PWM-channel through clk_get. if someone wants
> a clock, get it from clock subsystem, and the PWM channel here can
> request the clock as well. but i don't have plan to do that for the
> moment.
>
i am not sure whether i have described everything clear enough. the
point is if the bluetooth want a clock with 32KHz, it should want it
by clk_get(), but not get it from pwm_config. it is just a workaround.
the pwm is the concept of prima2 hardware, lcd can think it is asking
pwm, why is bluetooth thinking it is requesting a PWM? in the view of
bluetooth, the source is a clock not a PWM thing for backlight.

-barry