x86/hyperv/vtl: Use the wakeup mailbox to boot secondary CPUs

x86/hyperv/vtl: Use the wakeup mailbox to boot secondary CPUs

The hypervisor is an untrusted entity for TDX guests. It cannot be used
to boot secondary CPUs. The function hv_vtl_wakeup_secondary_cpu() cannot
be used.

Instead, the virtual firmware boots the secondary CPUs and places them in
a state to transfer control to the kernel using the wakeup mailbox. The
firmware enumerates the mailbox via either an ACPI table or a DeviceTree
node.

If the wakeup mailbox is present, the kernel updates the APIC callback
wakeup_secondary_cpu_64() to use it.

Reviewed-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: Dexuan Cui <dexuan@kernel.org>