x86: VMX: MSR_IA32_VMX_MISC[30] is not MBZ

MSR_IA32_VMX_MISC[30] tells whehter "VM entry allows injection of a
software interrupt, software exception, or privileged software exception
with an instruction length of 0".

In other words, it is not MBZ (must be zero), so do not check that it is
cleared.

Signed-off-by: Nadav Amit <namit@vmware.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>