KVM: SVM: Create trace events for VMGEXIT MSR protocol processing

Add trace events for entry to and exit from VMGEXIT MSR protocol
processing. The vCPU will be common for the trace events. The MSR
protocol processing is guided by the GHCB GPA in the VMCB, so the GHCB
GPA will represent the input and output values for the entry and exit
events, respectively. Additionally, the exit event will contain the
return code for the event.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Message-Id: <c5b3b440c3e0db43ff2fc02813faa94fa54896b0.1607620209.git.thomas.lendacky@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>