pwm: jz4740: Enable for all Ingenic SoCs

This driver works perfectly with all the versions of the SoCs from
Ingenic that are supported upstream.

This makes the driver usable on JZ4740, JZ4770 and JZ4780 SoCs.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>