[SPARC64]: Small Schizo PCI controller programming tweaks.

Use macro instead of magic value for Tomatillo discard-
timeout interrupt enable register bit.

Leave OBP programming PTO value unless Tomatillo and
version >= 0x2.

If no-bus-parking property is present, explicitly clear
PCICTRL_PARK bit.

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