(OPTION_INTR_NOPS): Define.
(gen_interrupt_nops): Default to FALSE.
(md_parse_opton): Add support for OPTION_INTR_NOPS.
(md_longopts): Add -mn.
(md_show_usage): Add -mn.
(msp430_operands): Generate NOPs for all MCUs not just 430Xv2.
* doc/c-msp430.c: Document -mn.