Drop kvm_mmu_extended_role.cr4_la57 now that mmu_role doesn't mask off
level, which already incorporates the guest's CR4.LA57 for a shadow MMU
by querying is_la57_mode().
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>