i386: Add L3 cache support to AMD CPUID4 emulation

With that an L3 cache is correctly reported in the cache information in /sys

With fixes from Andreas Herrmann and Dean Gaudet and Joachim Deguara

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>