xen/arm: introduce create_domUs

xen/arm: introduce create_domUs

Call a new function, "create_domUs", from setup_xen to start DomU VMs.

Introduce support for the "xen,domain" compatible node on device tree.
Create new DomU VMs based on the information found on device tree under
"xen,domain". Call construct_domU for each domain.

Introduce a simple global variable named max_init_domid to keep track of
the initial allocated domids. It holds the max domid among the initial
domains.

Move the discard_initial_modules after DomUs have been built.

First create domUs, then start dom0 -- no point in trying to start dom0
when the cpu is busy.

Signed-off-by: Stefano Stabellini <stefanos@xilinx.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
[julien: Add XEN_DOMCTL_CDF_hap_guest]
Reviewed-by: Julien Grall <julien.grall@arm.com>
CC: andrew.cooper3@citrix.com
CC: jbeulich@suse.com