Update function description per UEFI2.3d. The main changes include:

Update function description per UEFI2.3d. The main changes include:
1.    If string is a unicode string, its description doesn’t need to specify unicode word again, because by default, string is UCS-2 (Table 6) encoded.
2.    EFI_UNSUPPORTED return status is missing for EFI_EAP_PROTOCOL.SetDesiredAuthMethod() function.
3.    For LoadImage() service, EFI_ACCESS_DENIED return status is added, and EFI_SECURITY_VIOLATION return status description is updated.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@11305 6f19259b-4bc3-4df7-8a09-765794883524