target/i386: enumerate bit 56 of MSR_IA32_VMX_BASIC

On parts that enumerate IA32_VMX_BASIC MSR bit as 1, any exception vector
can be delivered with or without an error code if the other consistency
checks are satisfied.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

scripts/kvm/vmxcap

@@ -115,6 +115,7 @@ controls = [
             (50, 53): 'VMCS memory type',
             54: 'INS/OUTS instruction information',
             55: 'IA32_VMX_TRUE_*_CTLS support',
+            56: 'Skip checks on event error code',
             },
         msr = MSR_IA32_VMX_BASIC,
         ),