GitLab

* Update DMA & DMA lite channels to work on Pi 4 (HAL_IRQClear calls
needed)
* Fix DMAL_Abort / DMAL_Reset to reset the channel properly (register
muddle meant the old reset code wasn't doing anything - and wasn't a
particularly great way of resetting anyway)
* Fix DMAL_CurtailListTransfer not working very well
* Fix IRQ mapping of channels 11-14, allowing channels 12-14 to be used
* Implement support for Pi 4 DMA4 channels. On Pi 4 these are the only
channels we'll bother using, since DMA & DMA lite have annoying
restrictions on accessing RAM above 1GB