staging:iio:ad9834: Mark transfer buffers as __b16

Fixes the following warnings from sparse:
drivers/staging/iio/frequency/ad9834.c:45:26: warning: incorrect type in assignment (different base types)
drivers/staging/iio/frequency/ad9834.c:45:26: expected unsigned short [unsigned] [short] <noident>
drivers/staging/iio/frequency/ad9834.c:45:26: got restricted __be16 [usertype] <noident>
drivers/staging/iio/frequency/ad9834.c:47:26: warning: incorrect type in assignment (different base types)
drivers/staging/iio/frequency/ad9834.c:47:26: expected unsigned short [unsigned] [short] <noident>
drivers/staging/iio/frequency/ad9834.c:47:26: got restricted __be16 [usertype] <noident>
drivers/staging/iio/frequency/ad9834.c:59:18: warning: incorrect type in assignment (different base types)
drivers/staging/iio/frequency/ad9834.c:59:18: expected unsigned short [unsigned] data
drivers/staging/iio/frequency/ad9834.c:59:18: got restricted __be16 [usertype] <noident>
drivers/staging/iio/frequency/ad9834.c:100:26: warning: incorrect type in assignment (different base types)
drivers/staging/iio/frequency/ad9834.c:100:26: expected unsigned short [unsigned] data
drivers/staging/iio/frequency/ad9834.c:100:26: got restricted __be16 [usertype] <noident>
drivers/staging/iio/frequency/ad9834.c:108:26: warning: incorrect type in assignment (different base types)
drivers/staging/iio/frequency/ad9834.c:108:26: expected unsigned short [unsigned] data
drivers/staging/iio/frequency/ad9834.c:108:26: got restricted __be16 [usertype] <noident>
drivers/staging/iio/frequency/ad9834.c:122:26: warning: incorrect type in assignment (different base types)
drivers/staging/iio/frequency/ad9834.c:122:26: expected unsigned short [unsigned] data
drivers/staging/iio/frequency/ad9834.c:122:26: got restricted __be16 [usertype] <noident>
drivers/staging/iio/frequency/ad9834.c:131:26: warning: incorrect type in assignment (different base types)
drivers/staging/iio/frequency/ad9834.c:131:26: expected unsigned short [unsigned] data
drivers/staging/iio/frequency/ad9834.c:131:26: got restricted __be16 [usertype] <noident>
drivers/staging/iio/frequency/ad9834.c:194:26: warning: incorrect type in assignment (different base types)
drivers/staging/iio/frequency/ad9834.c:194:26: expected unsigned short [unsigned] data
drivers/staging/iio/frequency/ad9834.c:194:26: got restricted __be16 [usertype] <noident>
drivers/staging/iio/frequency/ad9834.c:387:18: warning: incorrect type in assignment (different base types)
drivers/staging/iio/frequency/ad9834.c:387:18: expected unsigned short [unsigned] data
drivers/staging/iio/frequency/ad9834.c:387:18: got restricted __be16 [usertype] <noident>

Signed-off-by: Lars-Peter Clausen <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/staging/iio/frequency/ad9834.h

···
 	 * DMA (thus cache coherency maintenance) requires the
 	 * transfer buffers to live in their own cache lines.
 	 */
-	unsigned short			data ____cacheline_aligned;
-	unsigned short			freq_data[2] ;
+	__be16				data ____cacheline_aligned;
+	__be16				freq_data[2];
 };