dmaengine: altera-msgdma: add OF support

This driver had no device tree support.

- add compatible field "altr,socfpga-msgdma"
- register dma controller with of_dma_controller_register

Reviewed-by: Stefan Roese <sr@denx.de>
Signed-off-by: Olivier Dautricourt <olivier.dautricourt@orolia.com>
Link: https://lore.kernel.org/r/7459635ba093d87b6bf12413cf7cfe09f6e3019b.1623251990.git.olivier.dautricourt@orolia.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>