Documentation/virtual/kvm: Update URL for AMD SEV API specification

The URL of [api-spec] in Documentation/virtual/kvm/amd-memory-encryption.rst
is no longer valid, replaced space with underscore.
Signed-off-by: NChristophe de Dinechin <dinechin@redhat.com>
Reviewed-by: NBrijesh Singh <brijesh.singh@amd.com>
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>

Documentation/virtual/kvm/amd-memory-encryption.rst

@@ -242,6 +242,6 @@ References
 ==========
 
 .. [white-paper] http://amd-dev.wpengine.netdna-cdn.com/wordpress/media/2013/12/AMD_Memory_Encryption_Whitepaper_v7-Public.pdf
-.. [api-spec] http://support.amd.com/TechDocs/55766_SEV-KM%20API_Specification.pdf
+.. [api-spec] http://support.amd.com/TechDocs/55766_SEV-KM_API_Specification.pdf
 .. [amd-apm] http://support.amd.com/TechDocs/24593.pdf (section 15.34)
 .. [kvm-forum]  http://www.linux-kvm.org/images/7/74/02x08A-Thomas_Lendacky-AMDs_Virtualizatoin_Memory_Encryption_Technology.pdf