cma: Add support for memory limits

Currently, when dynamically placing regions CMA will allow the memory
to be placed anywhere, including highmem. Due to system restrictions,
regions may need to be placed in a smaller range. Add support to
devicetree to allow these regions to have an upper bound on where they
will be placed.

Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
[skhiani@codeaurora.org: Resolve merge conflicts]
Signed-off-by: Susheel Khiani <skhiani@codeaurora.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>