Allow the SMT bit to be set/reset at boot, like the ALTIVEC bit.  This
means we will enable SMT on unknown cpus that support it.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>