KVM: selftests: Use "standard" min virtual address for Hyper-V pages

Use the de facto standard minimum virtual address for Hyper-V's hcall
params page.  It's the allocator's job to not double-allocate memory,
i.e. there's no reason to force different regions for the params vs.
hcall page.  This will allow adding a page allocation helper with a
"standard" minimum address.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622200529.3650424-6-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>