mm/memory.c: use helper macro min and max in unmap_mapping_range_tree()

Use helper macro min and max to help simplify the code logic.  Minor
readability improvement.

Link: https://lkml.kernel.org/r/20220224121134.35068-1-linmiaohe@huawei.comSigned-off-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memory.c

@@ -3350,12 +3350,8 @@ static inline void unmap_mapping_range_tree(struct rb_root_cached *root,
 	vma_interval_tree_foreach(vma, root, first_index, last_index) {
 		vba = vma->vm_pgoff;
 		vea = vba + vma_pages(vma) - 1;
-		zba = first_index;
-		if (zba < vba)
-			zba = vba;
-		zea = last_index;
-		if (zea > vea)
-			zea = vea;
+		zba = max(first_index, vba);
+		zea = min(last_index, vea);
 
 		unmap_mapping_range_vma(vma,
 			((zba - vba) << PAGE_SHIFT) + vma->vm_start,