MdeModulePkg/XhciDxe/Xhci: Don't check for invalid PSIV

MdeModulePkg/XhciDxe/Xhci: Don't check for invalid PSIV

PSID matching relies on comparing the PSIV against the PortSpeed
value. This patch stops edk2 from checking for a PSIV of 0, as it
is not valid; this reduces the number of register access by
approximately 6 per second.

Cc: Hao A Wu <hao.a.wu@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-by: Sean Rhodes <sean@starlabs.systems>
Reviewed-by: Hao A Wu <hao.a.wu@intel.com>