drivers: base: power: add proper SPDX identifiers on files that did not have them.

There were a few files in the driver core power code that did not have
SPDX identifiers on them, so fix that up.  At the same time, remove the
"free form" text that specified the license of the file, as that is
impossible for any tool to properly parse.

Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/power/trace.c

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * drivers/base/power/trace.c
  *
@@ -6,7 +7,6 @@
  * Trace facility for suspend/resume problems, when none of the
  * devices may be working.
  */
-
 #define pr_fmt(fmt) "PM: " fmt
 
 #include <linux/pm-trace.h>