microblaze/PCI: remove unused pci_flags

pci_flags is initialized to zero and never modified (I think this was just
copied from powerpc).  Therefore, "(pci_flags & XX)" is always false and
"!(pci_flags & XX)" is always true, and we can remove all references
to pci_flags.

CC: Michal Simek <monstr@monstr.eu>
CC: microblaze-uclinux@itee.uq.edu.au
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>