mips: dts: ingenic: x1000: Add PWM device tree node

Copied from the jz4740 devicetree and trimmed to 5 timers, which
is what the hardware supports.

Signed-off-by: Aidan MacDonald <aidanmacdonald.0x0@gmail.com>
Tested-by: 周琰杰 (Zhou Yanjie) <zhouyanjie@wanyeetech.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>