drivers: dma-contiguous: add initialization from device tree

drivers: dma-contiguous: add initialization from device tree

Add a function to create CMA region from previously reserved memory and
add support for handling 'shared-dma-pool' reserved-memory device tree
nodes.

Based on previous code provided by Josh Cartwright <[email protected]>

Signed-off-by: Marek Szyprowski <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Michal Nazarewicz <[email protected]>
Cc: Grant Likely <[email protected]>
Cc: Laura Abbott <[email protected]>
Cc: Josh Cartwright <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Kyungmin Park <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>