of/device: Merge of_platform_bus_probe()

Merge common code between PowerPC and microblaze.  This patch merges
the code that scans the tree and registers devices.  The functions
merged are of_platform_bus_probe(), of_platform_bus_create(), and
of_platform_device_create().

This patch also move the of_default_bus_ids[] table out of a Microblaze
header file and makes it non-static.  The device ids table isn't merged
because powerpc and microblaze use different default data.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
CC: Michal Simek <monstr@monstr.eu>
CC: Grant Likely <grant.likely@secretlab.ca>
CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
CC: Stephen Rothwell <sfr@canb.auug.org.au>
CC: microblaze-uclinux@itee.uq.edu.au
CC: linuxppc-dev@ozlabs.org