spi: dw-mid: change magic numbers to the constants

Instead of using magic numbers in the code we create a bit map definition of
the DMACR register and use it.

There is no functional change.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
diff --git a/drivers/spi/spi-dw.h b/drivers/spi/spi-dw.h
index 089fc4b..83a103a 100644
--- a/drivers/spi/spi-dw.h
+++ b/drivers/spi/spi-dw.h
@@ -74,6 +74,10 @@
 #define SPI_INT_RXFI			(1 << 4)
 #define SPI_INT_MSTI			(1 << 5)
 
+/* Bit fields in DMACR */
+#define SPI_DMA_RDMAE			(1 << 0)
+#define SPI_DMA_TDMAE			(1 << 1)
+
 /* TX RX interrupt level threshold, max can be 256 */
 #define SPI_INT_THRESHOLD		32