Rename HTVALID to CMP_LEGACY

AMD renamed the HTVALID CPUID flag to CMP_LEGACY and reverted its meaning. 
Follow this for /proc/cpuinfo

Needed for the followon CMP patches.
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>