Most architectures turn on PCI_COMMAND_IO and PCI_COMMAND_MEMORY in
pci_enable_device() when a driver claims the device. Sparc LEON did it in
pcibios_fixup_bus(), which is called during enumeration, before any drivers
are attached.
Implement pcibios_enable_device() for LEON so it will do the same as other
architectures. This implementation is copied verbatim from sparc64.