target/i386: cleanup eob handling of RSM

target/i386: cleanup eob handling of RSM

gen_helper_rsm cannot generate an exception, and reloads the flags.
So there's no need to spill cc_op and update cpu_eip, but on the
other hand cc_op must be reset to CC_OP_EFLAGS before returning.

It all works by chance, because by spilling cc_op before the call
to the helper, it becomes non-dirty and gen_eob will not overwrite
the CC_OP_EFLAGS value that is placed there by the helper.  But
let's clean it up.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>