iio: adis16400: Fix burst transfer for adis16448

The adis16448, unlike the other chips in this family, in addition to the
hardware channels also sends out the DIAG_STAT register in burst mode
before them. Handle that case by skipping over the first 2 bytes before we
pass the received data to the buffer.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Fixes: 76ada52f7f5d ("iio:adis16400: Add support for the adis16448")
Cc: <stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
diff --git a/drivers/iio/imu/adis16400.h b/drivers/iio/imu/adis16400.h
index 1e8fd2e..73b189c 100644
--- a/drivers/iio/imu/adis16400.h
+++ b/drivers/iio/imu/adis16400.h
@@ -139,6 +139,7 @@
 #define ADIS16400_NO_BURST		BIT(1)
 #define ADIS16400_HAS_SLOW_MODE		BIT(2)
 #define ADIS16400_HAS_SERIAL_NUMBER	BIT(3)
+#define ADIS16400_BURST_DIAG_STAT	BIT(4)
 
 struct adis16400_state;