platform_pwm_op( id, op, data ) did four unrelated tasks, switching on the
"op" parameter:
op==PLATFORM_PWM_OP_SET_CLOCK took a frequency and returned a frequency
op==PLATFORM_PWM_OP_GET_CLOCK took nothing returned a frequency
op==PLATFORM_PWM_OP_START and _STOP both took nothing and returned nothing
this patch replaces it with:
clock = platform_pwm_set_clock( id, clock)
clock = platform_pwm_get_clock( id )
platform_pwm_start( id ) and
platform_pwm_stop( id )
with resulting clarity in the documentation and smaller, faster code.
This does not affect the Lau interface.