We have not needed to end a TB for I/O since ba3e7926691
("icount: clean up cpu_can_io at the entry to the block").
We do not need to use exit_tb for singlestep, which only
means generate one insn per TB.
Which leaves only singlestep_enabled, which means raise a
debug trap after every TB, which does not use exit_tb,
which would leave the function mis-named.
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
cba201f4c7