Remove bio_cachep from slab.h

bio_cachep is no longer used it seems.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.19-rc5-mm2/include/linux/slab.h
===================================================================
--- linux-2.6.19-rc5-mm2.orig/include/linux/slab.h	2006-11-17 23:03:46.114062585 -0600
+++ linux-2.6.19-rc5-mm2/include/linux/slab.h	2006-11-17 23:03:51.817677214 -0600
@@ -302,7 +302,6 @@ extern kmem_cache_t	*names_cachep;
 extern kmem_cache_t	*files_cachep;
 extern kmem_cache_t	*filp_cachep;
 extern kmem_cache_t	*fs_cachep;
-extern kmem_cache_t	*bio_cachep;
 
 #endif	/* __KERNEL__ */