Add IOAPIC support for Intel 82371EB and fixup SMP on ASUS P2B-D.

Add IOAPIC support for Intel 82371EB and fixup SMP on ASUS P2B-D.

 - Add enable_intel_82093aa_ioapic() which enables IOAPIC usage in the
   Intel 82371EB southbridge (sets the proper chip-select) and sets an
   IOAPIC ID.

 - We only call enable_intel_82093aa_ioapic() if a board does "select IOAPIC"
   as on 82371EB-based boards the IOAPIC is an external chip (not integrated
   in the southbridge) and it's only populated on multi-CPU boards.
   That is, we cannot unconditionally enable it, only on SMP-capable boards.

 - Due to the reason explained above, remove "select IOAPIC" from
   src/southbridge/intel/i82371eb/Kconfig, and add it to
   src/mainboard/asus/p2b-d/Kconfig.

 - Also set CONFIG_MAX_PHYSICAL_CPUS to 2 on ASUS P2B-D. 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-D's romstage.c,
   that function is always called if either CONFIG_SMP and/or CONFIG_IOAPIC
   are set.

 - Rework ASUS P2B-D 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.

This is build-tested on ASUS P2B-D, and also boot-tested successfully there.
On Linux I now get two entries in /proc/cpuinfo (where only one appeared
before this patch), i.e. both populated CPUs are found.

Signed-off-by: Uwe Hermann <uwe@hermann-uwe.de>
Acked-by: Uwe Hermann <uwe@hermann-uwe.de>
git-svn-id: svn://svn.coreboot.org/coreboot/trunk@5998 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1