staging: hikey9xx: hi6421-spmi-pmic: update copyright notes

At PMIC subsystem, C89 comments are preferred over C99.
While here, also update the copyrights of the header file.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/5a86478c8ccb93d3105485b5f16e20e9c12e2196.1611949675.git.mchehab+huawei@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>