system: Extract target-specific globals to their own compilation unit

system: Extract target-specific globals to their own compilation unit

We shouldn't use target specific globals for machine properties.
These ones could be desugarized, as explained in [*]. While
certainly doable, not trivial nor my priority for now. Just move
them to a different file to clarify they are *globals*, like the
generic globals residing in system/globals.c.

Since arch_init.c was introduced using the MIT license (see commit
ad96090a01d), retain the same license for the new globals-target.c
file.

[*] https://lore.kernel.org/qemu-devel/e514d6db-781d-4afe-b057-9046c70044dc@redhat.com/

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20250305005225.95051-2-philmd@linaro.org>