Mptable related fixes for ASUS P2B-DS.

Mptable related fixes for ASUS P2B-DS.

 - Add "select IOAPIC" in the board's Kconfig file.

 - Set CONFIG_MAX_PHYSICAL_CPUS to 2 on the board. There are two
   CPU sockets (Slot 1) and each CPU can only have one core, multi-core CPUs
   didn't exist in that era (CONFIG_MAX_CPUS was set to 2 already).

 - Drop useless/duplicated enable_lapic() call from ASUS P2B-DS's romstage.c,
   that function is always called if either CONFIG_SMP and/or CONFIG_IOAPIC
   are set.

 - Rework ASUS P2B-DS mptable.c to fix a number of things:

   - Convert it to use mptable_write_buses() as all mptable.c files should do.

   - Fix incorrect IOAPICID (it's 0x11 for the external 82093AA IOAPIC).

   - Fix a bunch of hardcoded bus IDs, remove incorrect entries, etc.

Signed-off-by: Uwe Hermann <uwe@hermann-uwe.de>
Acked-by: Peter Stuge <peter@stuge.se>
git-svn-id: svn://svn.coreboot.org/coreboot/trunk@6004 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1