configfs: replace strncpy with memcpy

BugLink: https://bugs.launchpad.net/bugs/1810947

commit 1823342a upstream.

gcc 8.1.0 complains:

fs/configfs/symlink.c:67:3: warning:
	'strncpy' output truncated before terminating nul copying as many
	bytes from a string as its length
fs/configfs/symlink.c: In function 'configfs_get_link':
fs/configfs/symlink.c:63:13: note: length computed here

Using strncpy() is indeed less than perfect since the length of data to
be copied has already been determined with strlen(). Replace strncpy()
with memcpy() to address the warning and optimize the code a little.
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nobuhiro Iwamatsu <nobuhiro.iwamatsu@cybertrust.co.jp>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

fs/configfs/symlink.c

@@ -64,7 +64,7 @@ static void fill_item_path(struct config_item * item, char * buffer, int length)
 
 		/* back up enough to print this bus id with '/' */
 		length -= cur;
-		strncpy(buffer + length,config_item_name(p),cur);
+		memcpy(buffer + length, config_item_name(p), cur);
 		*(buffer + --length) = '/';
 	}
 }