arch/arm: domain build: let dom0 access I/O memory of mapped devices

arch/arm: domain build: let dom0 access I/O memory of mapped devices

Currently, dom0 is allowed access to the I/O memory ranges used
to access devices exposed to it, but it doesn't have those
ranges in its iomem_caps. This commit implements the correct
bookkeeping in the generic function which actually maps a
device's I/O memory to the domain, adding the ranges to the
domain's iomem_caps.

NOTE: This commit suffers from the following limitations;
      . with this patch, I/O memory ranges pertaining disabled
        devices are not mapped;
      . the "iomem" option could be used to map memory ranges that
        are not described in the device tree.
      In both these cases, this patch does not allow the domain
      the privileges needed to map the needed I/O memory ranges
      afterwards.

Signed-off-by: Arianna Avanzini <avanzini.arianna@gmail.com>
Acked-by: Ian Campbell <Ian.Campbell@eu.citrix.com>
Acked-by: Julien Grall <julien.grall@citrix.com>
Cc: Dario Faggioli <dario.faggioli@citrix.com>
Cc: Paolo Valente <paolo.valente@unimore.it>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Jan Beulich <JBeulich@suse.com>
Cc: Keir Fraser <keir@xen.org>
Cc: Tim Deegan <tim@xen.org>
Cc: Ian Jackson <Ian.Jackson@eu.citrix.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Eric Trudeau <etrudeau@broadcom.com>
Cc: Viktor Kleinik <viktor.kleinik@globallogic.com>