selinux: use kmem_cache for ebitmap

The allocated size for each ebitmap_node is 192byte by kzalloc().
Then, ebitmap_node size is fixed, so it's possible to use only 144byte
for each object by kmem_cache_zalloc().
It can reduce some dynamic allocation size.

Signed-off-by: Junil Lee <junil0814.lee@lge.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

security/selinux/ss/ebitmap.h

@@ -130,6 +130,9 @@ void ebitmap_destroy(struct ebitmap *e);
 int ebitmap_read(struct ebitmap *e, void *fp);
 int ebitmap_write(struct ebitmap *e, void *fp);
 
+void ebitmap_cache_init(void);
+void ebitmap_cache_destroy(void);
+
 #ifdef CONFIG_NETLABEL
 int ebitmap_netlbl_export(struct ebitmap *ebmap,
 			  struct netlbl_lsm_catmap **catmap);