accel/mshv: Add accelerator skeleton

Introduce the initial scaffold for the MSHV (Microsoft Hypervisor)
accelerator backend. This includes the basic directory structure and
stub implementations needed to integrate with QEMU's accelerator
framework.

Signed-off-by: Magnus Kulke <magnuskulke@linux.microsoft.com>
Link: https://lore.kernel.org/r/20250916164847.77883-8-magnuskulke@linux.microsoft.com
[Move include of linux/mshv.h in the per-target section; create
 include/system/mshv_int.h. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
5 files changed