staging: pi433: fix CamelCase for preambleLength variable

Fixes checkpatch warning:

  CHECK: Avoid CamelCase: <preambleLength>
Signed-off-by: Valentin Vidic <Valentin.Vidic@CARNet.hr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/pi433/rf69.c

@@ -590,7 +590,7 @@ int rf69_set_rssi_threshold(struct spi_device *spi, u8 threshold)
 	return rf69_write_reg(spi, REG_RSSITHRESH, threshold);
 }
 
-int rf69_set_preamble_length(struct spi_device *spi, u16 preambleLength)
+int rf69_set_preamble_length(struct spi_device *spi, u16 preamble_length)
 {
 	int retval;
 	u8 msb, lsb;
@@ -598,8 +598,8 @@ int rf69_set_preamble_length(struct spi_device *spi, u16 preambleLength)
 	/* no value check needed - u16 exactly matches register size */
 
 	/* calculate reg settings */
-	msb = (preambleLength & 0xff00) >> 8;
-	lsb = (preambleLength & 0xff);
+	msb = (preamble_length & 0xff00) >> 8;
+	lsb = (preamble_length & 0xff);
 
 	/* transmit to chip */
 	retval = rf69_write_reg(spi, REG_PREAMBLE_MSB, msb);

drivers/staging/pi433/rf69.h

@@ -44,7 +44,7 @@ int rf69_set_ook_threshold_dec(struct spi_device *spi, enum threshold_decrement
 int rf69_set_dio_mapping(struct spi_device *spi, u8 DIONumber, u8 value);
 bool rf69_get_flag(struct spi_device *spi, enum flag flag);
 int rf69_set_rssi_threshold(struct spi_device *spi, u8 threshold);
-int rf69_set_preamble_length(struct spi_device *spi, u16 preambleLength);
+int rf69_set_preamble_length(struct spi_device *spi, u16 preamble_length);
 int rf69_enable_sync(struct spi_device *spi);
 int rf69_disable_sync(struct spi_device *spi);
 int rf69_set_fifo_fill_condition(struct spi_device *spi, enum fifo_fill_condition fifo_fill_condition);