Add possibility to use library with different DMA_IRQ

[negis02]

Thanks for grate library. I hawed a issue to get work this library together with Adafruit_NeoPXL8, because both libraries using same DMA_IRQ. so i edit DmxInput.cpp file in Pico-DMX:

dma_hw->ints0 = 1u << i;
dma_channel_set_irq0_enabled(_dma_chan, true);
irq_set_exclusive_handler(DMA_IRQ_0, dmxinput_dma_handler);
irq_set_enabled(DMA_IRQ_0, true);

to

dma_hw->ints1 = 1u << i;
dma_channel_set_irq1_enabled(_dma_chan, true);
irq_set_exclusive_handler(DMA_IRQ_1, dmxinput_dma_handler);
irq_set_enabled(DMA_IRQ_1, true);

Now I'm able to control animation patterns of 4000 WS2812 pixels at 35FPS (4 strips 1000LED length) by DMX signal in my project.