proc: make struct struct map_files_info::len unsigned int

Linux doesn't support 4GB+ filenames in /proc, so unsigned long is too
much.

MOV r64, r/m64 is larger than MOV r32, r/m32.

Link: http://lkml.kernel.org/r/20161029161123.GG1246@avx2Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/proc/base.c

@@ -1967,7 +1967,7 @@ static int map_files_get_link(struct dentry *dentry, struct path *path)
 
 struct map_files_info {
 	fmode_t		mode;
-	unsigned long	len;
+	unsigned int	len;
 	unsigned char	name[4*sizeof(long)+2]; /* max: %lx-%lx\0 */
 };