drivers: base: Add GENERIC_MEM_NODE for nodes online during boot

NUMA systems are unable to use GENERIC_CPU_DEVICES, as nodes must
be registered before the existing register_cpu() calls can create
node symlinks. The nodes can't be registered before postcore_initcall()
as they depend on the node bus.

arm64, ia64 and x86 all call register_one_node() for each online node.
Add GENERIC_MEM_NODE to do this before GENERIC_CPU_DEVICES needs the
data. Move register_node_type() to happen this early to. This now
matches the time that the cpu bus is created in cpu_dev_init().

This will allow topology_init()s contents to be moved to core code for
arm64, ia64 and x86.

Signed-off-by: James Morse <james.morse@arm.com>