target-tricore: fix msub32_q producing the wrong overflow bit

The inversion of the overflow bit as a special case, which was needed for the
madd32_q instructions, does not apply for msub32_q instructions. So remove it.

Signed-off-by: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Message-Id: <1432289758-6250-3-git-send-email-kbastian@mail.uni-paderborn.de>
