staging: pi433: Use the correct style for SPDX License Identifier

staging: pi433: Use the correct style for SPDX License Identifier

This patch corrects the SPDX License Identifier style in
header files related to pi433 radio module drivers.
It assigns explicit block comment to the SPDX License Identifier.

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>
Link: https://lore.kernel.org/r/20200208083621.GA3797@nishad
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>