d400 should NoDecode on x86-64

[mborgerson]

Description

On x86-32, this decodes to:

0:  d4 00                   aam    0x0

On x86-64 this should be an invalid instruction byte sequence, however pyvex will decode it properly.

Steps to reproduce the bug

In [8]: import pyvex, archinfo; pyvex.lift(b'\xd4\x00', 0, archinfo.ArchAMD64())
Out[8]: IRSB <0x2 bytes, 1 ins., <Arch AMD64 (LE)>> at 0x0

Environment

pyvex @ git+https://github.com/angr/pyvex@d8f69b03fd4408c4b84214ed1998f4f3fd070da9

Additional context

No response