target/i386: [tcg] Port to disas_log

Incrementally paves the way towards using the generic instruction translation
loop.

Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>
Reviewed-by: Emilio G. Cota <cota@braap.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Message-Id: <150002243497.22386.8888053391875656102.stgit@frigg.lan>
[rth: Move tb->size computation and use that result.]
Signed-off-by: Richard Henderson <rth@twiddle.net>
