Replace boilerplate notice for unversioned GPL to SPDX tag for GPL 1.0+.
For ne2k-pci.c, only add SPDX tag and keep the boilerplate instead,
since the boilerplate notes that it must be preserved.

Cc: David A. Hinds <dahinds@users.sourceforge.net>
Cc: Donald Becker <becker@scyld.com>
Cc: Alan Cox <alan@linux.intel.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Richard Fontana <rfontana@redhat.com>
Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>