test suite: use %zu to print size_t

On 32-bit, we can't use %lu to print a size_t variable and gcc warns us
about it.  Shame it doesn't warn about it on 64-bit.

Link: https://lkml.kernel.org/r/20250403003311.359917-1-Liam.Howlett@oracle.com
Fixes: cc86e0c ("radix tree test suite: add support for slab bulk APIs")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: Matthew Wilcox (Oracle)

tools/testing/shared/linux.c

@@ -150,7 +150,7 @@ void kmem_cache_free(struct kmem_cache *cachep, void *objp)
 void kmem_cache_free_bulk(struct kmem_cache *cachep, size_t size, void **list)
 {
 	if (kmalloc_verbose)
-		pr_debug("Bulk free %p[0-%lu]\n", list, size - 1);
+		pr_debug("Bulk free %p[0-%zu]\n", list, size - 1);
 
 	pthread_mutex_lock(&cachep->lock);
 	for (int i = 0; i < size; i++)
@@ -168,7 +168,7 @@ int kmem_cache_alloc_bulk(struct kmem_cache *cachep, gfp_t gfp, size_t size,
 	size_t i;
 
 	if (kmalloc_verbose)
-		pr_debug("Bulk alloc %lu\n", size);
+		pr_debug("Bulk alloc %zu\n", size);
 
 	pthread_mutex_lock(&cachep->lock);
 	if (cachep->nr_objs >= size) {