1. updated "the Bus Driver that creates all of its child handles on the first call...

1. updated "the Bus Driver that creates all of its child handles on the first call to Start()" not to create any child handle if RemainingDeviepath is the End of Device Path Node, per UEFI 2.3.

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