cpu: move Qemu[Thread|Cond] setup into common code

cpu: move Qemu[Thread|Cond] setup into common code

Aside from the round robin threads this is all common code. By
moving the halt_cond setup we also no longer need hacks to work around
the race between QOM object creation and thread creation.

It is a little ugly to free stuff up for the round robin thread but
better it deal with its own specialises than making the other
accelerators jump through hoops.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Message-ID: <20240530194250.1801701-3-alex.bennee@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>