machine: Provide a function to check the dynamic sysbus allowlist

machine: Provide a function to check the dynamic sysbus allowlist

Provide a new function dynamic_sysbus_dev_allowed() which checks the
per-machine list of permitted dynamic sysbus devices and returns a
boolean result indicating whether the device is allowed.  We can use
this in the implementation of validate_sysbus_device(), but we will
also need it so that machine hotplug callbacks can validate devices
rather than assuming that any sysbus device might be hotpluggable
into the platform bus.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Message-id: 20210325153310.9131-3-peter.maydell@linaro.org