fs: Use new numeric setenv functions

Use setenv_ulong(), setenv_hex() and setenv_addr() in fs/

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/fs/fs.c b/fs/fs.c
index 023e7ef..2c9f2c5 100644
--- a/fs/fs.c
+++ b/fs/fs.c
@@ -256,7 +256,6 @@
 	unsigned long bytes;
 	unsigned long pos;
 	int len_read;
-	char buf[12];
 	unsigned long time;
 
 	if (argc < 2)
@@ -308,8 +307,7 @@
 	}
 	puts("\n");
 
-	sprintf(buf, "0x%x", len_read);
-	setenv("filesize", buf);
+	setenv_hex("filesize", len_read);
 
 	return 0;
 }