Parse zero or more assembler output operands, separated by commas.
(parse-?-asm-output-operands parstate) → (mv erp outputs span new-parstate)
If the next token is an open square bracket or a string literal, there must be at least one assembler output operand, so we call the function that parses one or more assembler output operands. If the next token is not an open square bracket or a string literal, then there are no assembler output operands; we return an irrelevant span in this case, which callers do not use.