Pull more xen updates from Juergen Gross:
- a patch to fix a build warning
- a cleanup of no longer needed code in the Xen event handling
- a small series for the Xen grant driver avoiding high order
allocations and replacing an insane global limit by a per-call one
- a small series fixing Xen frontend/backend module referencing
* tag 'for-linus-5.5b-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
xen-blkback: allow module to be cleanly unloaded
xen/xenbus: reference count registered modules
xen/gntdev: switch from kcalloc() to kvcalloc()
xen/gntdev: replace global limit of mapped pages by limit per call
xen/gntdev: remove redundant non-zero check on ret
xen/events: remove event handling recursion detection