percpu: Cast away printk format warning

On 32-bit systems which don't happen to implicitly define or cast
VMALLOC_START and/or VMALLOC_END to long in their arch headers, the
printk in the percpu code will cause a warning to be emitted:

mm/percpu.c: In function 'pcpu_embed_first_chunk':
mm/percpu.c:1648: warning: format '%lx' expects type 'long unsigned int',
        but argument 3 has type 'unsigned int'

So add an explicit cast to unsigned long here.
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Tejun Heo <tj@kernel.org>

mm/percpu.c

@@ -1646,8 +1646,8 @@ int __init pcpu_embed_first_chunk(size_t reserved_size, size_t dyn_size,
 	/* warn if maximum distance is further than 75% of vmalloc space */
 	if (max_distance > (VMALLOC_END - VMALLOC_START) * 3 / 4) {
 		pr_warning("PERCPU: max_distance=0x%zx too large for vmalloc "
-			   "space 0x%lx\n",
-			   max_distance, VMALLOC_END - VMALLOC_START);
+			   "space 0x%lx\n", max_distance,
+			   (unsigned long)(VMALLOC_END - VMALLOC_START));
 #ifdef CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK
 		/* and fail if we have fallback */
 		rc = -EINVAL;