target/i386: Save cc_op before loop insns

We forgot to update cc_op before these branch insns,
which lead to losing track of the current eflags.

Buglink: https://bugs.launchpad.net/qemu/+bug/1888165


Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20200720154028.477457-1-richard.henderson@linaro.org>