AMD/agesa: Add functions for AMD PCI IRQ routing

Port the changes that were made in amd/cimx to amd/agesa
as were done in:
   commit c93a75a5ab067f86104028b74d92fc54cb939cd5
   Author: Mike Loptien <mike.loptien@se-eng.com>
   Date:   Fri Jun 6 15:16:29 2014 -0600

      AMD/CIMx: Add functions for AMD PCI IRQ routing

This change also moves the PCI INT functions to
southbridge/amd so that they can be used by CIMX and
AGESA. The amd/persimmon board is updated for this
change.

Signed-off-by: Dave Frodin <dave.frodin@se-eng.com>
Change-Id: I525be90f9cf8e825e162d53a7ecd1e69c6e27637
Reviewed-on: http://review.coreboot.org/6065
Tested-by: build bot (Jenkins)
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>