target/m68k: fix m68k_cpu_dump_state()

Display correctly the Trace bits for 680x0
(2 bits instead of 1 for Coldfire).

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20180104012913.30763-18-laurent@vivier.eu>