add cpuf to the nix mkfile

Reference: /n/atom/patch/applied2013/cpufmk
Date: Sun Dec 29 14:45:16 CET 2013
Signed-off-by: quanstro@quanstro.net

--- /sys/src/nix/k10/mkfile	Sun Dec 29 14:45:07 2013
+++ /sys/src/nix/k10/mkfile	Sun Dec 29 14:45:07 2013
@@ -1,5 +1,5 @@
 CONF=cpu
-CONFLIST=cpu cpud term termd
+CONFLIST=cpu cpud cpuf term termd
 
 objtype=amd64
 </$objtype/mkfile