VT-d: section placement and type adjustments

VT-d: section placement and type adjustments

With x2APIC requiring iommu_supports_eim() to return true, we can
adjust a few conditonals such that both it and
platform_supports_x2apic() can be marked __init. For the latter as
well as for platform_supports_intremap() also change the return types
to bool_t.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Yang Zhang <yang.z.zhang@intel.com>