Friended dma_ch1_isr

Moved matrixCalculations to private, and friended dma_ch1_isr.
Mostly equivalent register changes

Replaced register assignments to logic masking to not clear previously
initalized  states. Moved DMA_Channel 1 priority as a #define and set
it to FE instead of FF to allow one slot for other applications. Lastly
Replaced (1<<7) with equivalent DMA_CR_EMLM and replaced 0 with
equivalent DMAMUX_DISABLE.