ARM: at91/dt: at91sam9m10g45ek PWM leds polarity is inversed

The real polarity of the LEDs is inversed. The led is between 3.3v and the PWM.
It was working before because the driver was getting the duty cycle calculation
wrong.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>