net: usb: Add SMSC copyright to smsc95xx driver

This driver was upstreamed without an SMSC copyright, even thought it seems
that SMSC was the original author.

See the kernel version for a code comparison:

http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=2f7ca802bdae2ca41022618391c70c2876d92190



It's not clear who actually moved this code, or whether the kernel was the
original source, or somewhere else, but it probably should still have the
SMSC copyright.

Signed-off-by: Simon Glass <sjg@chromium.org>

drivers/usb/eth/smsc95xx.c

 /*
  * Copyright (c) 2011 The Chromium OS Authors.
  * Copyright (C) 2009 NVIDIA, Corporation
+ * Copyright (C) 2007-2008 SMSC (Steve Glendinning)
  *
  * SPDX-License-Identifier:	GPL-2.0+
  */