The others changes include:
a. Check RemainingDevicePath at beginning of Supported(), make sure it has been verified before Start() is called.
b. Check IO protocol firstly rather than EfiDevicePathProtocolGuid, reduce the times entering into Start() function because EfiDevicePathProtocolGuid existed on most of handle.
2. roll back serial drivers not to create child device, if the device speicifed by remainingdevicepath cannot find in the created devices list.
git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@9267 6f19259b-4bc3-4df7-8a09-765794883524
