staging: pi433: Remove the unused FREQUENCY define

FREQUENCY is not being used, delete its comment.

Signed-off-by: Shahar Avidar <ikobh7@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20240227221204.534131-5-ikobh7@gmail.com


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