staging: pi433: Move FIFO_THRESHOLD define to source file

FIFO_THRESHOLD is only being used in pi433_if.c source files.
Signed-off-by: Shahar Avidar <ikobh7@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20240227221204.534131-6-ikobh7@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/pi433/pi433_if.c

@@ -49,6 +49,7 @@
 #define N_PI433_MINORS		BIT(MINORBITS) /*32*/	/* ... up to 256 */
 #define MAX_MSG_SIZE		900	/* min: FIFO_SIZE! */
 #define MSG_FIFO_SIZE		65536   /* 65536 = 2^16  */
+#define FIFO_THRESHOLD	15		/* bytes */
 #define NUM_DIO			2
 
 static dev_t pi433_dev;

drivers/staging/pi433/rf69.h

@@ -12,7 +12,6 @@
 #include "rf69_registers.h"
 
 #define FIFO_SIZE	66		/* bytes */
-#define FIFO_THRESHOLD	15		/* bytes */
 
 u8 rf69_read_reg(struct spi_device *spi, u8 addr);
 int rf69_get_version(struct spi_device *spi);