* Xen hypervisor reserved-memory binding

Expose one or more memory regions as reserved-memory to the guest
virtual machine. Typically, a region is configured at VM creation time
to be a shared memory area across multiple virtual machines for
communication among them.

For each of these pre-shared memory regions, a range is exposed under
the /reserved-memory node as a child node. Each range sub-node is named
xen-shmem@<address> and has the following properties:

- compatible:
	compatible = "xen,shared-memory-v1"

- reg:
	the base guest physical address and size of the shared memory region

- xen,offset: (borrower VMs only)
	64 bit integer offset within the owner virtual machine's shared
	memory region used for the mapping in the borrower VM.

- xen,id:
	a string that identifies the shared memory region as specified in
	the VM config file
