ANDPS, like all others PS (Packed Single precision floats) instructions,
need Ym: they don't use the 0x66 prefix.

From the manual:

    NP 0F 54 /r        ANDPS xmm1, xmm2/m128

NP meaning, quoting the manual:

  NP - Indicates the use of 66/F2/F3 prefixes (beyond those already part
  of the instructions opcode) are not allowed with the instruction.

And indeed, the same instruction prefixed by 0x66 is ANDPD.

Updates #14069

Change-Id: If312a6f1e77113ab8c0febe66bdb1b4171e41e0a
Reviewed-on: https://go-review.googlesource.com/42090Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>