rpmsg: virtio_rpmsg_bus: Switch to SPDX license identifier

Use the appropriate SPDX license identifier in the virtio rpmsg
bus driver source file and drop the previous boilerplate license
text.

Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/rpmsg/virtio_rpmsg_bus.c

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * Virtio-based remote processor messaging bus
  *
@@ -6,15 +7,6 @@
  *
  * Ohad Ben-Cohen <ohad@wizery.com>
  * Brian Swetland <swetland@google.com>
- *
- * This software is licensed under the terms of the GNU General Public
- * License version 2, as published by the Free Software Foundation, and
- * may be copied, distributed, and modified under those terms.
- *
- * 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.
  */
 
 #define pr_fmt(fmt) "%s: " fmt, __func__