xen/intr: implement aarch64 variant of xen_arch_intr.c

[ehem_freebsd_m5p.com]

Summary

This is the core of the architecture-dependent portion of the Xen
event channel/interrupt handling. Originally implemented by Julien Grall
in 2015, but heavily updated for submission by Elliott Mitchell in 2021.

This is based on the core FreeBSD interrupt code. While the additional
functionality provided by intrng could be nice, only the core is
actually required.

Submitted by: Elliott Mitchell <[e-mail]>
Original implementation: Julien Grall <[e-mail]>, 2015-10-21 07:18:56
Original implementation: Julien Grall <[e-mail]>, 2015-11-02 04:31:56

[ehem_freebsd_m5p.com]

This is the main aarch64 architecture file for Xen. It is simply binding the Xen event channel/interrupt core to the FreeBSD interrupt core.

[ehem_freebsd_m5p.com]

Updating xen_arch_intr_execute_handlers() to return boolean. This is to match with updates elsewhere.

[ehem_freebsd_m5p.com]

Turning a number of the ARM64 compatibility functions into inlines.