iio: adc: ltc2309: Fix endian type passed to be16_to_cpu()

Picked up by sparse.

Cc: Liam Beguin <liambeguin@gmail.com>
Reviewed-by: Liam Beguin <liambeguin@gmail.com>
Link: https://patch.msgid.link/20240624193210.347434-1-jic23@kernel.orgSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/ltc2309.c

@@ -103,7 +103,7 @@ static int ltc2309_read_raw_channel(struct ltc2309 *ltc2309,
 				    unsigned long address, int *val)
 {
 	int ret;
-	u16 buf;
+	__be16 buf;
 	u8 din;
 
 	din = FIELD_PREP(LTC2309_DIN_CH_MASK, address & 0x0f) |