xen: arm: handle initrd addresses above the 4G boundary

xen: arm: handle initrd addresses above the 4G boundary

The Xgene platform has no RAM below 4G.

The /chosen/linux,initrd-* properties do not have "reg" semantics and
therefore #*-size are not used when interpreting. Instead they are are simply
numbers which are interpreted according to the properties length.

Fix this both when parsing the entry in the host DTB and when creating the
dom0 DTB. For dom0 we simply hardcode a 64-bit size, this is acceptable
even for a 32-bit guest.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Julien Grall <julien.grall@linaro.org>