Reduce the boilerplate required for each target.  At the same time,
move the test for breakpoint after calling tcg_gen_insn_start.

Note that arm and aarch64 do not use cpu_breakpoint_test, but still
move the inline test down after tcg_gen_insn_start.
Reviewed-by: NAurelien Jarno <aurelien@aurel32.net>
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NRichard Henderson <rth@twiddle.net>