ada: Remove -gnateE information message for noncontiguous enumeration type

It is very confusing for the user because it does not make any reference
to the source code but only to details of the underlying implementation.

gcc/ada/ChangeLog:
	* gcc-interface/trans.cc (Raise_Error_to_gnu) <CE_Invalid_Data>:
	Do not the generate range information if the value is a call to a
	Rep_To_Pos function.