Staging: rtl8192e: Replace license text with SPDX identifier

- adds the SPDX GPL-2.0 license identifier which solves the checkpatch.pl warning
- Removed license boilerplate text
- Issue found with checkpatch.pl warning:
  "WARNING: Missing or malformed SPDX-License-Identifier tag in line 1"
Signed-off-by: Bhanusree Pola <bhanusreemahesh@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8192e/dot11d.h

+/* SPDX-License-Identifier: GPL-2.0 */
 /******************************************************************************
  * Copyright(c) 2008 - 2010 Realtek Corporation. All rights reserved.
  *
- * This program is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
- * more details.
- *
- * The full GNU General Public License is included in this distribution in the
- * file called LICENSE.
- *
  * Contact Information:
  * wlanfae <wlanfae@realtek.com>
  ******************************************************************************/