hw/arm/boot: arm_load_kernel implemented as a machine init done notifier

hw/arm/boot: arm_load_kernel implemented as a machine init done notifier

Device tree nodes for the platform bus and its children dynamic sysbus
devices are added in a machine init done notifier. To load the dtb once,
after those latter nodes are built and before ROM freeze, the actual
arm_load_kernel existing code is moved into a notifier notify function,
arm_load_kernel_notify. arm_load_kernel now only registers the
corresponding notifier.

Machine files that do not support platform bus stay unchanged. Machine
files willing to support dynamic sysbus devices must call arm_load_kernel
before sysbus-fdt arm_register_platform_bus_fdt_creator to make sure
dynamic sysbus device nodes are integrated in the dtb.

Signed-off-by: Eric Auger <[email protected]>
Reviewed-by: Shannon Zhao <[email protected]>
Reviewed-by: Alexander Graf <[email protected]>
Reviewed-by: Alex Bennée <[email protected]>
Message-id: 1433244554[email protected]
Signed-off-by: Peter Maydell <[email protected]>