MdeModulePkg: XhciDxe: Prevent illegal memory access in XhcSetHsee

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1206

Newly added XhcSetHsee() routine reads 4 bytes into
a UINT16 variable causing issues on PCIE and NonDiscoverable
Xhci controllers. Fix that.

Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Fei1 Wang <fei1.wang@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Marcin Wojtas <mw@semihalf.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>

MdeModulePkg/Bus/Pci/XhciDxe/XhciReg.c

@@ -609,7 +609,7 @@ XhcSetHsee (
                         PciIo,
                         EfiPciIoWidthUint16,
                         PCI_COMMAND_OFFSET,
-                        sizeof (XhciCmd),
+                        sizeof (XhciCmd) / sizeof (UINT16),
                         &XhciCmd
                         );
   if (!EFI_ERROR (Status)) {