vfio/container: Rename vfio_init_container to vfio_set_iommu

vfio/container: Rename vfio_init_container to vfio_set_iommu

vfio_container_init() and vfio_init_container() names are confusing
especially when we see vfio_init_container() calls vfio_container_init().

vfio_container_init() operates on base container which is consistent
with all routines handling 'VFIOContainerBase *' ops.

vfio_init_container() operates on legacy container and setup IOMMU
context with ioctl(VFIO_SET_IOMMU).

So choose to rename vfio_init_container to vfio_set_iommu to avoid
the confusion.

No functional change intended.

Suggested-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>