We have not needed to end a TB for I/O since ba3e792669
("icount: clean up cpu_can_io at the entry to the block").
In use_goto_tb, the check for singlestep_enabled is in the
generic translator_use_goto_tb. In s390x_tr_tb_stop, the
check for singlestep_enabled is in the preceding do_debug test.
Which leaves only FLAG_MASK_PER: fold that test alone into
the two callers of use_exit tb.
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>