staging: pi433: Remove unused driver

Marcus started a project in 2016 to bring the pi433 alive. One project
was funded successfully but the second not. So only a few pi433 got sold
to early adaptors during this time that ended late 2017. There is a
simple user space program available for a demo with the pi433 but that
does not use this driver.

The driver is unused since 2018. No description or user space application
to use it can be found. To bring it alive the device tree needs to be
adjusted manually.

The last patch reviewed by Marcus was in June 2018, last patch tested
was in July 2017.

No response since 27. March 2024 regarding the removal of the driver.
Remove unused driver because of the above named reasons.

Link: https://lore.kernel.org/linux-staging/c4c5ab38-8c67-4c21-86bc-f4f3c06be358@gmail.com/
Link: https://www.kickstarter.com/projects/1292669042/pi433-a-radio-module-funkmodul-for-raspberry-pi
Link: https://www.kickstarter.com/projects/1292669042/smarthome-pi/comments
Link: https://www.pi433.de/en.html


Signed-off-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
Cc: Marcus Wolf <marcus.wolf@wolf-entwicklungen.de>
Link: https://lore.kernel.org/r/20240421195717.GA10943@matrix-ESPRIMO-P710


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