Documentation: KVM: Add SPDX-License-Identifier tag

+new file mode 100644
+WARNING: Missing or malformed SPDX-License-Identifier tag in line 1
+#27: FILE: Documentation/virt/kvm/x86/errata.rst:1:

Opportunistically update all other non-added KVM documents and
remove a new extra blank line at EOF for x86/errata.rst.
Signed-off-by: Like Xu <likexu@tencent.com>
Message-Id: <20220406063715.55625-5-likexu@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Documentation/virt/kvm/vcpu-requests.rst

+.. SPDX-License-Identifier: GPL-2.0
+
 =================
 KVM VCPU Requests
 =================

Documentation/virt/kvm/x86/amd-memory-encryption.rst

+.. SPDX-License-Identifier: GPL-2.0
+
 ======================================
 Secure Encrypted Virtualization (SEV)
 ======================================

Documentation/virt/kvm/x86/errata.rst

+.. SPDX-License-Identifier: GPL-2.0
 
 =======================================
 Known limitations of CPU virtualization
@@ -36,4 +37,3 @@ Nested virtualization features
 ------------------------------
 
 TBD
-

Documentation/virt/kvm/x86/running-nested-guests.rst

+.. SPDX-License-Identifier: GPL-2.0
+
 ==============================
 Running nested guests with KVM
 ==============================