KVM: selftests: Unconditionally allocate EPT tables in memslot 0

Drop the EPTP memslot param from all EPT helpers and shove the hardcoded
'0' down to the vm_phy_page_alloc() calls.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622200529.3650424-14-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>