accel/tcg: Drop signness in tracing in cputlb.c

We are already inconsistent about whether or not
MO_SIGN is set in trace_mem_get_info.  Dropping it
entirely allows some simplification.

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>