SUNRPC: Add SPDX IDs to some net/sunrpc/auth_gss/ files

Files under net/sunrpc/auth_gss/ do not yet have SPDX ID tags.
This directory is somewhat complicated because most of these files
have license boilerplate that is not strictly GPL 2.0.

In this patch I add ID tags where there is an obvious match. The
less recognizable licenses are still under research.

For reference, SPDX IDs added in this patch correspond to the
following license text:

GPL-2.0         https://spdx.org/licenses/GPL-2.0.html
GPL-2.0+        https://spdx.org/licenses/GPL-2.0+.html
BSD-3-Clause    https://spdx.org/licenses/BSD-3-Clause.html

Cc: Simo Sorce <[email protected]>
Cc: Kate Stewart <[email protected]>
Signed-off-by: Chuck Lever <[email protected]>
Signed-off-by: Anna Schumaker <[email protected]>
diff --git a/net/sunrpc/auth_gss/auth_gss.c b/net/sunrpc/auth_gss/auth_gss.c
index 3d1fbd6..fda454c 100644
--- a/net/sunrpc/auth_gss/auth_gss.c
+++ b/net/sunrpc/auth_gss/auth_gss.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: BSD-3-Clause
 /*
  * linux/net/sunrpc/auth_gss/auth_gss.c
  *
@@ -8,34 +9,8 @@
  *
  *  Dug Song       <[email protected]>
  *  Andy Adamson   <[email protected]>
- *
- *  Redistribution and use in source and binary forms, with or without
- *  modification, are permitted provided that the following conditions
- *  are met:
- *
- *  1. Redistributions of source code must retain the above copyright
- *     notice, this list of conditions and the following disclaimer.
- *  2. Redistributions in binary form must reproduce the above copyright
- *     notice, this list of conditions and the following disclaimer in the
- *     documentation and/or other materials provided with the distribution.
- *  3. Neither the name of the University nor the names of its
- *     contributors may be used to endorse or promote products derived
- *     from this software without specific prior written permission.
- *
- *  THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
- *  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
- *  MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
- *  DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
- *  FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
- *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
- *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
- *  BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
- *  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
- *  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
- *  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/types.h>