layerscape: fix get_device_file() function of restool

layerscape: fix get_device_file() function of restool

The restool failed to work with current gcc-7.3.0-musl.
This patch is to add a restool fix-up patch to fix
multiple problems encountered in the get_device_file()
function:
 - The deprecated atoi() function is replaced by strtoul
 - An invalid memory access was being performed by using
 memory from dir->d_name even after closedir(). This is
 fixed by a strdup() on the device filename.
 - Also, error prints now print any relevant error code.

Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>