nVMX: Pass exit reason enum to print_vmexit_info()

Take the exit reason as a parameter when printing VM-Exit info instead
of rereading it from the VMCS.  Opportunistically clean up the related
printing.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>