staging: pi433: Remove a duplicated FIFO_SIZE define

FIFO_SIZE is being used in both rf69.c & pi433_if.c source files.
It is also already defined in rf69.h header file.

Signed-off-by: Shahar Avidar <ikobh7@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20240227221204.534131-2-ikobh7@gmail.com


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