zsmalloc: remove null check from destroy_handle_cache()

We can pass a NULL cache pointer to kmem_cache_destroy(), because it
NULL-checks its argument now.  Remove redundant test from
destroy_handle_cache().

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/zsmalloc.c

@@ -288,8 +288,7 @@ static int create_handle_cache(struct zs_pool *pool)
 
 static void destroy_handle_cache(struct zs_pool *pool)
 {
-	if (pool->handle_cachep)
-		kmem_cache_destroy(pool->handle_cachep);
+	kmem_cache_destroy(pool->handle_cachep);
 }
 
 static unsigned long alloc_handle(struct zs_pool *pool)