target-i386: factor gen_op_set_cc_op/tcg_gen_discard_tl around computing flags

target-i386: factor gen_op_set_cc_op/tcg_gen_discard_tl around computing flags

Before computing flags we need to store the cc_op to memory.  Move this
to gen_compute_eflags_c and gen_compute_eflags rather than doing it all
over the place.

Alo, after computing the flags in cpu_cc_src we are in EFLAGS mode.
Set s->cc_op and discard cpu_cc_dst in gen_compute_eflags, rather than
doing it all over the place.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Richard Henderson <rth@twiddle.net>