predicates.md (mem_or_easy_const_operand): Delete.

        * config/rs6000/predicates.md (mem_or_easy_const_operand): Delete.
        (reg_or_none500mem_operand): New predicate.
        (zero_reg_mem_operand): New predicate.
        * config/rs6000/rs6000.md (extendsfdf2): Change operand1 predicate
        to reg_or_none500mem_operand.
        (extendsfdf2_fpr): Add MEM alternative.
        (extenddftf2_internal): Change operand2 predicate to
        zero_reg_mem_operand.

From-SVN: r96390