MSP430: Fix relocation overflow when using #lo(EXP) macro

MSP430: Fix relocation overflow when using #lo(EXP) macro

gas/ChangeLog:

2020-01-15  Jozef Lawrynowicz  <jozef.l@mittosystems.com>

	* config/tc-msp430.c (CHECK_RELOC_MSP430): Always generate 430X
	relocations when the target is 430X, except when extracting part of an
	expression.
	(msp430_srcoperand): Adjust comment.
	Initialize the expp member of the msp430_operand_s struct as
	appropriate.
	(msp430_dstoperand): Likewise.
	* testsuite/gas/msp430/msp430.exp: Run new test.
	* testsuite/gas/msp430/reloc-lo-430x.d: New test.
	* testsuite/gas/msp430/reloc-lo-430x.s: New test.

include/ChangeLog:

2020-01-15  Jozef Lawrynowicz  <jozef.l@mittosystems.com>

	* opcode/msp430.h (enum msp430_expp_e): New.
	(struct msp430_operand_s): Add expp member to struct.

ld/ChangeLog:

2020-01-15  Jozef Lawrynowicz  <jozef.l@mittosystems.com>

	* testsuite/ld-msp430-elf/msp430-elf.exp: Run new test.
	* testsuite/ld-msp430-elf/reloc-lo-430x.s: New test.