arm64: hyperv: Use SMCCC to detect hypervisor presence

arm64: hyperv: Use SMCCC to detect hypervisor presence

The arm64 Hyper-V startup path relies on ACPI to detect
running under a Hyper-V compatible hypervisor. That
doesn't work on non-ACPI systems.

Hoist the ACPI detection logic into a separate function. Then
use the vendor-specific hypervisor service call (implemented
recently in Hyper-V) via SMCCC in the non-ACPI case.

Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Link: https://lore.kernel.org/r/20250428210742.435282-3-romank@linux.microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <20250428210742.435282-3-romank@linux.microsoft.com>