unicore32/PCI: adjust section annotations for pcibios_setup()

Make pcibios_setup() consistently use the "__init" section annotation.

Acked-by: Guan Xuetao <gxt@mprc.pku.edu.cn>
Signed-off-by: Myron Stowe <myron.stowe@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>