Pull xen fixes from Juergen Gross:
"This contains two cleanup patches and a small series for supporting
reloading the Xen block backend driver"
* tag 'for-linus-5.5b-rc3-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
xen/grant-table: remove multiple BUG_ON on gnttab_interface
xen-blkback: support dynamic unbind/bind
xen/interface: re-define FRONT/BACK_RING_ATTACH()
xenbus: limit when state is forced to closed
xenbus: move xenbus_dev_shutdown() into frontend code...
xen/blkfront: Adjust indentation in xlvbd_alloc_gendisk