Merge tag 'xen-arm64-3.1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/sstabellini/xen into upstream

Introduce Xen support to ARM64

* tag 'xen-arm64-3.1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/sstabellini/xen:
  MAINTAINERS: add myself as arm64/xen maintainer
  arm64/xen: introduce CONFIG_XEN and hypercall.S on ARM64
  arm64/xen: use XEN_IO_PROTO_ABI_ARM on ARM64
  arm64/xen: implement ioremap_cached on arm64
  arm64/xen: introduce asm/xen header files on arm64
  arm/xen: define xen_remap as ioremap_cached