Persimmon: Change MPTable to use mainboard IRQ routing

With the addition of the mainboard PCI IRQ routing tables
for AMD Persimmon, the MPTables can be set to use this
information to accurately reflect the real hardware settings
of the system.  Additionally, the IOAPIC gets defined before
the MPTable gets generated so the settings can be read
directly from the IOAPIC registers instead of 'guessing' at
them as was done before.

Change-Id: I96ec046a2208eddf4b5e442214ff43d2a349ca4d
Signed-off-by: Mike Loptien <mike.loptien@se-eng.com>
Reviewed-on: http://review.coreboot.org/5878
Tested-by: build bot (Jenkins)
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-by: Marc Jones <marc.jones@se-eng.com>