powerpc/83xx: factor out the common codes of setup arch functions

Factor out the common codes of setup arch functions to a separate
function. It does make no sense to print a board specific info
in setup arch functions, so use a more general one.

For ASP8347E board, there is no pci device node. So it is safe to
invoke mpc83xx_setup_pci() in its setup arch function even there is
no such invocation in its original setup arch function.

Signed-off-by: Kevin Hao <haokexin@gmail.com>
Signed-off-by: Scott Wood <oss@buserror.net>