vfio/{iommufd,container}: Remove caps::aw_bits

vfio/{iommufd,container}: Remove caps::aw_bits

Remove caps::aw_bits which requires the bcontainer::iova_ranges being
initialized after device is actually attached. Instead defer that to
.get_cap() and call vfio_device_get_aw_bits() directly.

This is in preparation for HostIOMMUDevice::realize() being called early
during attach_device().

Suggested-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>