proc: use "unsigned int" in proc_fill_cache()

All those lengths are unsigned as they should be.

Link: http://lkml.kernel.org/r/20180423213751.GC9043@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/proc/fd.c b/fs/proc/fd.c
index 05b9893..81882a1 100644
--- a/fs/proc/fd.c
+++ b/fs/proc/fd.c
@@ -248,7 +248,7 @@ static int proc_readfd_common(struct file *file, struct dir_context *ctx,
 		struct file *f;
 		struct fd_data data;
 		char name[10 + 1];
-		int len;
+		unsigned int len;
 
 		f = fcheck_files(files, fd);
 		if (!f)