staging: netlogic: Add SPDX-License-Identifier tag at the top

Adds the SPDX GPL-2.0 or BSD-2-clause license identifier,
which solves the checkpatch.pl warnings: "WARNING: Missing
or malformed SPDX-License-Identifier tag in line 1".

Signed-off-by: Bhagyashri Dighole <digholebhagyashri@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>