Sync patch r14251 from main trunk.
MdeMdeModulePkg/UsbBusDxe: Fixed a possible memory leak bug .

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/branches/UDK2010.SR1@14253 6f19259b-4bc3-4df7-8a09-765794883524