sparc32,leon: added LEON-common low-level PCI routines

The LEON architecture does not have a BIOS or bootloader that
initializes PCI for us, instead Linux generic PCI layer is used
to set up resources and IRQ.

Signed-off-by: Daniel Hellstrom <daniel@gaisler.com>
Signed-off-by: David S. Miller <davem@davemloft.net>