iommu/vt-d: Allow to flush more than 4GB of device TLBs

The shift qi_flush_dev_iotlb() is done on an int, which
limits the mask to 32 bits. Make the mask 64 bits wide so
that more than 4GB of address range can be flushed at once.

Signed-off-by: Joerg Roedel <jroedel@suse.de>