xen/arm: Map mmio-sram nodes as un-cached memory

xen/arm: Map mmio-sram nodes as un-cached memory

Map mmio-sram nodes as un-cached memory. If the node
has set the no-memory-wc property, we map it as device.

The DTS bindings for mmio-sram nodes can be found in the
Linux tree under Documentation/devicetree/bindings/sram/sram.txt.

Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Acked-by: Julien Grall <julien.grall@arm.com>