vtd: Fix flush for SRTP and SIRTP set

vtd: Fix flush for SRTP and SIRTP set

SRTP (Set Root Table Pointer) operation must be set before enable or
re-enable DMA remapping. And after set it, software must globally
invalidate the context-cache and then globally invalidate the
IOTLB. This is required to ensure hardware uses only the remapping
structures referenced by the new root-table pointer, and not stale
cached entries. Similarly, SIRTP (Set Interrupt Remap Table Pointer)
operation must be set before enable or re-enable Interrupt
remapping, and after set it, software must globally invalidate the
interrupt entry cache. This patch adds global context and iotlb
flush after set root entry, and globally flushs interrupt entry
cache before enabling Interrupt remapping. And remove the
iommu_flush_all in iommu_resume becuase it becomes redundant after
adds flush for SRTP in init_vtd_hw.

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