Message type for path related calls.

- Updated system calls VFS_ACCESS, VFS_CHDIR, VFS_CHMOD, VFS_CHROOT,
                        VFS_MKDIR, VFS_OPEN, VFS_RMDIR, VSF_UNLINK

 - Removed M3_STRING and M3_LONG_STRING, which are tied to a specific
   "generic" message, and replaced where needed with M_PATH_STRING_MAX,
   which is tied to the mess_lc_vfs_path message.

Change-Id: If287c74f5ece937b9431e5d95b5b58a3c83ebff1

lib/libusb/usb.c

@@ -132,7 +132,7 @@ int usb_init(char *name)
 
 	msg.m_type = USB_RQ_INIT;
 
-	strncpy(msg.USB_RB_INIT_NAME, name, M3_LONG_STRING);
+	strncpy(msg.USB_RB_INIT_NAME, name, M_PATH_STRING_MAX);
 	
 	res = ipc_sendrec(hcd_ep, &msg);