powerpc/5200: update contact email

My 'pengutronix' address is defunct for years. Merge the entries and use
the proper contact address.
Signed-off-by: Wolfram Sang <wsa@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200502142642.18979-1-wsa@kernel.org

arch/powerpc/boot/dts/pcm032.dts

@@ -3,9 +3,7 @@
  * phyCORE-MPC5200B-IO (pcm032) board Device Tree Source
  *
  * Copyright (C) 2006-2009 Pengutronix
- * Sascha Hauer <s.hauer@pengutronix.de>
- * Juergen Beisert <j.beisert@pengutronix.de>
- * Wolfram Sang <w.sang@pengutronix.de>
+ * Sascha Hauer, Juergen Beisert, Wolfram Sang <kernel@pengutronix.de>
  */
 
 /include/ "mpc5200b.dtsi"