pwm: jz4740: Add support for X1000 SoC

The X1000 has the same TCU / PWM hardware as other Ingenic SoCs,
but it has only 5 channels.

Signed-off-by: Aidan MacDonald <aidanmacdonald.0x0@gmail.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>