FROMGIT: dt-bindings: of: Add restricted DMA pool

Introduce the new compatible string, restricted-dma-pool, for restricted
DMA. One can specify the address and length of the restricted DMA memory
region by restricted-dma-pool in the reserved-memory node.

Signed-off-by: Claire Chang <tientzu@chromium.org>
Tested-by: Stefano Stabellini <sstabellini@kernel.org>
Tested-by: Will Deacon <will@kernel.org>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
(cherry picked from commit b12fe999 swiotlb/devel/for-linus-5.15)
Signed-off-by: Will Deacon <willdeacon@google.com>
Bug: 190591509
Change-Id: Ibd4b39e176dddbe5f91396118edc713520dd11e1