xtensa: make map_suffix_reloc_to_operator return operatorT

xtensa: make map_suffix_reloc_to_operator return operatorT

It always returns an element of the enum operatorT, so it should be clearer to
make that the return type.

gas/ChangeLog:

2016-05-24  Trevor Saunders  <tbsaunde+binutils@tbsaunde.org>

	* config/tc-xtensa.c (struct suffix_reloc_map): Change type of field
	operator to operatorT.
	(map_suffix_reloc_to_operator): Change return type to operatorT.