of: remove asm/of_device.h

It is mostly unused now.  Sparc has a few defines left in it, but they
can be moved to other headers.  Removing this header means that new
architectures adding CONFIG_OF support don't need to also add this
header file.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: David S. Miller <davem@davemloft.net>