Tighten the constraints for warning about NOPs for the MSP 430 ISA, so NOPs are only...

Tighten the constraints for warning about NOPs for the MSP 430 ISA, so NOPs are only inserted/warned about when needed.  Specifically: 430 and 430x ISA require a NOP after DINT.  Only the 430x ISA requires NOP before EINT.  Only the 430x ISA requires NOP after every EINT. CPU42 errata.

	* config/tc-msp430.c (is_dint): New.
	(is_eint): New.
	(gen_nop): New.
	(warn_eint_nop): New.
	(warn_unsure_interrupt): New.
	(msp430_operands): Determine the effect MOV #N,SR insns have on
	interrupt state.
	Only emit NOP warnings for 430 ISA in certain situations.
	(msp430_md_end): Only warn about an EINT at the end of the file
	if NOP warnings are enabled.
	* testsuite/gas/msp430/bad.l: Adjust expected output for new warnings.
	* testsuite/gas/msp430/msp430.exp: Run new tests.
	* testsuite/gas/msp430/nop-dint-430.d: New.
	* testsuite/gas/msp430/nop-dint-430.l: New.
	* testsuite/gas/msp430/nop-dint-430x-ignore.d: New.
	* testsuite/gas/msp430/nop-dint-430x-silent.d: New.
	* testsuite/gas/msp430/nop-dint-430x.d: New.
	* testsuite/gas/msp430/nop-dint-430x.l: New.
	* testsuite/gas/msp430/nop-dint.s: New.
	* testsuite/gas/msp430/nop-eint-430.d: New.
	* testsuite/gas/msp430/nop-eint-430.l: New.
	* testsuite/gas/msp430/nop-eint-430x-ignore.d: New.
	* testsuite/gas/msp430/nop-eint-430x-silent.d: New.
	* testsuite/gas/msp430/nop-eint-430x.d: New.
	* testsuite/gas/msp430/nop-eint-430x.l: New.
	* testsuite/gas/msp430/nop-eint.s: New.
	* testsuite/gas/msp430/nop-int-430.d: New.
	* testsuite/gas/msp430/nop-int-430.l: New.
	* testsuite/gas/msp430/nop-int-430x-silent.d: New.
	* testsuite/gas/msp430/nop-int-430x.d: New.
	* testsuite/gas/msp430/nop-int-430x.l: New.
	* testsuite/gas/msp430/nop-int.s: New.