xen/control: print warning on call of xctrl_suspend()
Presently suspend/resume and migration aren't supported on Xen/ARM. As
such this shouldn't ever occur.
This likely applies to future Xen architectures (RISC-V) and
xctrl_suspend() needs dependency on intr_machdep.h fixed.
Submitted by: Elliott Mitchell <email@example.com>
Reviewed by: royger
Differential Revision: https://reviews.freebsd.org/D29599