msp430: fix BR instruction behavior and register-indirect @Rn disasse… #60

Job	Run time
ci / Build	3m 1s
ci / Lint	56s
ci / Test (0)	1m 13s
ci / Test (1)	1m 19s
ci / Test (2)	1m 8s
ci / Test (3)	49s
ci / Test (4)	1m 40s
ci / Test (5)	48s
ci / Test (6)	1m 5s
ci / Test (7)	53s
ci / Test (8)	1m 3s
ci / Test (9)	1m 50s
ci / Publish Unit Tests Results	1s
	15m 46s

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