net: dpaa2: Use the correct style for SPDX License Identifier

This patch corrects the SPDX License Identifier style in
header files related to DPAA2 Ethernet driver supporting
Freescale SoCs with DPAA2. For C header files
Documentation/process/license-rules.rst mandates C-like comments
(opposed to C source files where C++ style should be used)

Changes made by using a script provided by Joe Perches here:
https://lkml.org/lkml/2019/2/7/46.

Suggested-by: Joe Perches <joe@perches.com>
Signed-off-by: Nishad Kamdar <nishadkamdar@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>