iio: chemical: bme680: use BME680_NUM_CHANNELS for scan buffer

Use BME680_NUM_CHANNELS instead of the hardcoded channel count
in the scan buffer.

This avoids use of a magic number and improves code readability
and maintainability.

Suggested-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Nikhil Gautam <nikhilgtr@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

Author: Nikhilgtr

drivers/iio/chemical/bme680_core.c

@@ -128,7 +128,7 @@ struct bme680_data {
 	u16 heater_temp;
 
 	struct {
-		s32 chan[4];
+		s32 chan[BME680_NUM_CHANNELS];
 		aligned_s64 ts;
 	} scan;