set up interrupt values for the southbridge, and add a function to

set up interrupt values for the southbridge, and add a function to
manage them. Make pci_level_irq global. Add value settings for OLPC
rev_a board. Comment out no-longer-needed code in olpc mainboard.c
-- it is replaced by the settings in Config.lb, and the support
in cs5536.c

git-svn-id: svn://svn.coreboot.org/coreboot/trunk@2328 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1