Currently hyperv-iommu is implemented in a x86 specific way, for
example, apic is used. So make the HYPERV_IOMMU Kconfig depend on X86
as a preparation for enabling HyperV on architecture other than x86.
Cc: Lan Tianyu <Tianyu.Lan@xxxxxxxxxxxxx>
Cc: Michael Kelley <mikelley@xxxxxxxxxxxxx>
Cc: linux-hyperv@xxxxxxxxxxxxxxx
Signed-off-by: Boqun Feng (Microsoft) <boqun.feng@xxxxxxxxx>