They are use less, and may generate compiling warnings, so remove them
(microblaze, arc, arm64, and unicore32 have already defined PCI_IOBASE).

The related warnings (with allmodconfig under microblaze):

  CC [M]  drivers/net/fddi/skfp/skfddi.o
  In file included from drivers/net/fddi/skfp/skfddi.c:95:0:
  drivers/net/fddi/skfp/h/skfbi.h:151:0: warning: "PCI_IOBASE" redefined
   #define PCI_IOBASE 0xffffff00L  /* Bit 31..8:  I/O Base address */
   ^
  In file included from include/linux/io.h:22:0,
                   from include/linux/pci.h:31,
                   from drivers/net/fddi/skfp/skfddi.c:82:
  ./arch/microblaze/include/asm/io.h:33:0: note: this is the location of the previous definition
   #define PCI_IOBASE ((void __iomem *)_IO_BASE)
   ^
Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>