x86/shim: Short circuit control/hardware checks in PV_SHIM_EXCLUSIVE builds

x86/shim: Short circuit control/hardware checks in PV_SHIM_EXCLUSIVE builds

The net diffstat is:
  add/remove: 0/13 grow/shrink: 25/129 up/down: 6297/-20469 (-14172)

With the following objects/functions removed entirely:
  iommu_hwdom_none                               1       -      -1
  hwdom_max_order                                4       -      -4
  extra_hwdom_irqs                               4       -      -4
  ctldom_max_order                               4       -      -4
  acpi_c1e_quirk                                43       -     -43
  hvm_pirq_eoi                                  62       -     -62
  max_order                                     94       -     -94
  conring_puts                                 104       -    -104
  propagate_node                               119       -    -119
  mmio_ro_emulate_ops                          224       -    -224
  mmcfg_intercept_ops                          224       -    -224
  pci_cfg_ok                                   295       -    -295
  p2m_lock                                     546       -    -546

And the following reduced to stubs:
  arch_iommu_hwdom_init                        852       2    -850
  p2m_add_foreign                              880      16    -864

This patch also has the unintended but useful consequence of stopping
hardware_dom= functionality from being usable (in at least PV_SHIM_EXCLUSIVE
builds).

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Wei Liu <wl@xen.org>
Tested-by: Sergey Dyasli <sergey.dyasli@citrix.com>