m68k/pci: Drop useless pcibios_setup()

The PCI core supplies a weak pcibios_setup() implementation that is
identical to the m68k implementation.  Remove the m68k version since it is
unnecessary.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Greg Ungerer <gerg@linux-m68k.org>