MdeModulePkg/XhciDxe: Fix Aligned Page Allocation

While allocating pages aligned at an alignment higher than
4K, allocate memory taking into consideration the padding
required for that alignment. The calls to free pages takes
care of this already.

Signed-off-by: Ashish Singhal <ashishsingha@nvidia.com>
Reviewed-by: Hao A Wu <hao.a.wu@intel.com>

MdeModulePkg/Bus/Pci/XhciDxe/UsbHcMem.c

@@ -662,7 +662,7 @@ UsbHcAllocateAlignedPages (
                       PciIo,
                       AllocateAnyPages,
                       EfiBootServicesData,
-                      Pages,
+                      RealPages,
                       &Memory,
                       0
                       );