Problematic behaviour was added in commit a97f262ed (r26067), and
commit c39812d1b (r46193) converted to RtlUpcaseUnicodeString() call.
This was modifying the caller's given string. This is not really
a good practice to do so just to make display fancier.
For example, IopInitializeBuiltinDriver(), that calls the display
function, also uses the passed ServiceName later after.
Because IopDisplayLoadingMessage() executes only in SOS mode,
uppercasing the ServiceName in one case but not the other would
implicitly modify the observable OS behaviour.
IopSuffixUnicodeString() is adapted to be similar to RtlPrefixUnicodeString().
475098c8b1