pwm: atmel-hlcdc: Add errata handling for sama5d4

sama5d4 SoC also has an errata on the HLCDC PWM. It is the same as the
sama5d3 that is forbidding the use of div1 prescaler.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>