staging: pi433: fix validation for min bit rate supported by the device

rf69 datasheets establishes that the minimum supported bit rate is
1.2 kbps regardless of modulation.

this patch replaces the errouneous validation with the correct value

Acked-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Paulo Miguel Almeida <paulo.miguel.almeida.rodenas@gmail.com>
Link: https://lore.kernel.org/r/20220118230413.GA4859@mail.google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/pi433/rf69.c

@@ -226,14 +226,12 @@ int rf69_set_modulation_shaping(struct spi_device *spi,
 int rf69_set_bit_rate(struct spi_device *spi, u16 bit_rate)
 {
 	int retval;
-	u32 bit_rate_min;
 	u32 bit_rate_reg;
 	u8 msb;
 	u8 lsb;
 
 	// check input value
-	bit_rate_min = F_OSC / 8388608; // 8388608 = 2^23;
-	if (bit_rate < bit_rate_min) {
+	if (bit_rate < 1200) {
 		dev_dbg(&spi->dev, "setBitRate: illegal input param");
 		return -EINVAL;
 	}