libertas_tf: avoid warning about pr_fmt redefinition

Also includes a minor cleanup regarding quotation of a standard kernel
header file...

Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/libertas_tf/cmd.c

@@ -7,7 +7,8 @@
  *  the Free Software Foundation; either version 2 of the License, or (at
  *  your option) any later version.
  */
-#include "deb_defs.h"
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
 #include "libertas_tf.h"
 
 static const struct channel_range channel_ranges[] = {