clk: sunxi-ng: Use the correct style for SPDX License Identifier

This patch corrects the SPDX License Identifier style
in header files related to Clock Drivers for Allwinner SoCs.
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: Stephen Boyd <sboyd@kernel.org>