[SPARC64] PCI: Consolidate PCI access code into pci_common.c

All the sun4u controllers do the same thing to compute the physical
I/O address to poke, and we can move the sun4v code into this common
location too.

This one needs a bit of testing, in particular the Sabre code had some
funny stuff that would break up u16 and/or u32 accesses into pieces
and I didn't think that was needed any more.  If it is we need to find
out why and add back code to do it again.

Signed-off-by: David S. Miller <davem@davemloft.net>