Librem 14's power and charge LEDs work together, as they share a single
physical hole.  Effectively, they just change the color of a single
indicator controlled by a shared PWM.

Manage the charge LEDs as part of the same strategy.  Common code now
sets a desired power or charge LED state, and the 'leds' strategy
works out which LED to light based on the desired state.  Other boards
can employ different strategies when the power/charge LEDs are
separate, etc.

Rename the 'twosided' strategy to 'combined' to reflect that the key
behavior is combining the power/charge LEDs.

Signed-off-by: Jonathon Hall <jonathon.hall@puri.sm>