pwm: atmel: Remove useless symbolic definitions

The values that these symbols define are only assigned to the per-SoC
structure where the context is clear, so there's no need for the extra
symbolic name.

Acked-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>