net: update NXP copyright text

NXP Legal insists that the following are not fine:

- Saying "NXP Semiconductors" instead of "NXP", since the company's
  registered name is "NXP"

- Putting a "(c)" sign in the copyright string

- Putting a comma in the copyright string

The only accepted copyright string format is "Copyright <year-range> NXP".

This patch changes the copyright headers in the networking files that
were sent by me, or derived from code sent by me.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>
diff --git a/drivers/net/dsa_sandbox.c b/drivers/net/dsa_sandbox.c
index 4b62670..235f2f2 100644
--- a/drivers/net/dsa_sandbox.c
+++ b/drivers/net/dsa_sandbox.c
@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0+
 /*
- * Copyright 2019-2021 NXP Semiconductors
+ * Copyright 2019-2021 NXP
  */
 
 #include <asm/eth.h>