percpu: use VMALLOC_TOTAL instead of VMALLOC_END - VMALLOC_START

vmalloc already gives a useful macro to calculate the total vmalloc
size. Use it.
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
Signed-off-by: Tejun Heo <tj@kernel.org>

mm/percpu.c

@@ -1686,10 +1686,10 @@ int __init pcpu_embed_first_chunk(size_t reserved_size, size_t dyn_size,
 	max_distance += ai->unit_size;
 
 	/* warn if maximum distance is further than 75% of vmalloc space */
-	if (max_distance > (VMALLOC_END - VMALLOC_START) * 3 / 4) {
+	if (max_distance > VMALLOC_TOTAL * 3 / 4) {
 		pr_warning("PERCPU: max_distance=0x%zx too large for vmalloc "
 			   "space 0x%lx\n", max_distance,
-			   (unsigned long)(VMALLOC_END - VMALLOC_START));
+			   VMALLOC_TOTAL);
 #ifdef CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK
 		/* and fail if we have fallback */
 		rc = -EINVAL;