cpu/intel/slot_1: Init L2 cache on SECC(2) CPUs.

cpu/intel/slot_1: Init L2 cache on SECC(2) CPUs.

Bring from coreboot v1 support for initializing L2 cache on Slot 1
Pentium II/III CPUs, code names Klamath, Deschutes and Katmai.

Build tested on ASUS P2B-LS and P3B-F. Boot tested on P2B-LS with
Pentium III 600MHz, Katmai core.

Also add missing include of model_68x in slot_1, to address a
similar problem fixed for model_6bx by r5945.

Also change Deschutes CPU init sequence to match Katmai.

Change-Id: I502e8481d1a20f0a2504685e7be16b57f59c8257
Signed-off-by: Keith Hui <buurin@gmail.com>
Reviewed-on: http://review.coreboot.org/122
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>