usb: host: xhci: Stricter conditional for Z1 system models for Compliance Mode Patch

This minor patch creates a more stricter conditional for the Z1 sytems for applying
the Compliance Mode Patch, this to avoid the quirk to be applied to models that
contain a "Z1" in their dmi product string but are different from Z1 systems.

This patch should be backported to stable kernels as old as 3.2, that
contain the commit 71c731a296f1b08a3724bd1b514b64f1bda87a23 "usb: host:
xhci: Fix Compliance Mode on SN65LVPE502CP Hardware"

Signed-off-by: Alexis R. Cortes <alexis.cortes@ti.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: stable@vger.kernel.org