cma: Remove restriction on region names 

CMA currently restricts region names to 'region@x'. Devicetree
does not support the same value of x to be used multiple times.
This means that the devicetree cannot have multiple regions
be dynamically placed (x = 0). Remove the naming restriction
for CMA regions.

Change-Id: If647f8d7e6323497952431ae5b8cae05ba17af50
Signed-off-by: Laura Abbott <lauraa@codeaurora.org