x86/hvm: remove default ioreq server

x86/hvm: remove default ioreq server

My recent patch [1] to qemu-xen-traditional removes the last use of the
'default' ioreq server in Xen. (This is a catch-all ioreq server that is
used if no explicitly registered I/O range is targetted).

This patch can be applied once that patch is committed, to remove the
(>100 lines of) redundant code in Xen.

NOTE: The removal of the special case for HVM_PARAM_DM_DOMAIN in
      hvm_allow_set_param() is not directly related to removal of
      default ioreq servers. It could have been cleaned up at any time
      after commit 9a422c03 "x86/hvm: stop passing explicit domid to
      hvm_create_ioreq_server()". It is now added to the new
      deprecated sets introduced by this patch.

[1] https://lists.xenproject.org/archives/html/xen-devel/2018-08/msg00270.html

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>