hw/arm/sysbus-fdt: helpers for platform bus nodes addition

This new C module will be used by ARM machine files to generate
platform bus node and their dynamic sysbus device tree nodes.

Dynamic sysbus device node addition is done in a machine init
done notifier. arm_register_platform_bus_fdt_creator does the
registration of this latter and is supposed to be called by
ARM machine files that support platform bus and their dynamic
sysbus. Addition of dynamic sysbus nodes is done only if the
user did not provide any dtb.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Eric Auger <eric.auger@linaro.org>
Reviewed-by: Shannon Zhao <zhaoshenglong@huawei.com>
Reviewed-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 1433244554-12898-2-git-send-email-eric.auger@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>