#3211 bitfields with absolute addresses crash ds390 backend

[Philipp Klaus Krause]

While adding tests from Visenri's patch #373, I noticed that some of them crash the ds390 backend:

tests/bitfields-bits1.c
tests/bitfields-checks.c
tests/bitfields-dead-loop.c

I'll add the tests later today (disabled for ds390), so they can be used to reproduce this bug.