KVM: svm: drop explicit return value of kvm_vcpu_map

if kvm_vcpu_map returns non zero value, error path should be triggered
regardless of the exact returned error value.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20221025124741.228045-21-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>