Introduce function to check if the requested mode can use hw control in
preparation for hw control support. Currently everything is handled in
software so can_hw_control will always return false.

Add knob with the new value hw_control in trigger_data struct to
set hw control possible. Useful for future implementation to implement
in set_baseline_state() the required function to set the requested mode
using LEDs hw control ops and in other function to reject set if hw
control is currently active.
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>