hw/i386/intel_iommu: Fix struct VTDInvDescIEC on big endian hosts

hw/i386/intel_iommu: Fix struct VTDInvDescIEC on big endian hosts

On big endian hosts, we need to reverse the bitfield order in the
struct VTDInvDescIEC, just like it is already done for the other
bitfields in the various structs of the intel-iommu device.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20230802135723.178083-4-thuth@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
(cherry picked from commit 4572b22cf9ba432fa3955686853c706a1821bbc7)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>