x2APIC/VT-d: improve interrupt remapping and queued invalidation enabling and disabling

x2APIC/VT-d: improve interrupt remapping and queued invalidation enabling and disabling

x2APIC depends on interrupt remapping, so interrupt remapping needs to
be enabled before x2APIC. Usually x2APIC is not enabled
(x2apic_enabled=0) when enable interrupt remapping, although x2APIC
will be enabled later. So it needs to pass a parameter to set
interrupt mode in intremap_enable, instead of checking
x2apic_enable. This patch adds a parameter "eim" to intremap_enable to
achieve it.  Interrupt remapping and queued invalidation are already
enabled when enable x2apic, so it needn't to enable them again when
setup iommu. This patch checks if interrupt remapping and queued
invalidation are already enable or not, and won't enable them if
already enabled. It does the similar in disabling, that's to say don't
disable them if already disabled.

Signed-off-by: Weidong Han <weidong.han@intel.com>