sparc: move of_device common code to of_device_common

This patch moves code common to of_device_32.c and of_device_64.c into
of_device_common.h and of_device_common.c.

The only functional difference is in sparc32 where of_bus_default_map is
used in place of of_bus_sbus_map because they are equivelent.

There is still room for further code consolidation with some minor
refactoring.

Boot tested on sparc32 and compile tested on sparc64.

Signed-off-by: Robert Reif <reif@earthlink.net>
Signed-off-by: David S. Miller <davem@davemloft.net>