Don't rely on the 'VM-exit instruction length' field in the VMCS to always
have an accurate length on an EPT violation. This is not needed by the
instruction decoding code because it also has to work with AMD/SVM that
does not provide a valid instruction length on a Nested Page Fault.

In collaboration with: Leon Dang (ldang@nahannisys.com)
Discussed with: grehan
MFC after: 1 week