spi: atmel_spi: Use GENMASK

Replace numeric mask hexcodes with GENMASK macro
in atmel_spi

Cc: Bo Shen <voice.shen@atmel.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Jagan Teki <jteki@openedev.com>

drivers/spi/atmel_spi.h

@@ -59,7 +59,7 @@
 #define ATMEL_SPI_CSRx_CSAAT		BIT(3)
 #define ATMEL_SPI_CSRx_BITS(x)		((x) << 4)
 #define ATMEL_SPI_CSRx_SCBR(x)		((x) << 8)
-#define ATMEL_SPI_CSRx_SCBR_MAX		0xff
+#define ATMEL_SPI_CSRx_SCBR_MAX		GENMASK(7, 0)
 #define ATMEL_SPI_CSRx_DLYBS(x)		((x) << 16)
 #define ATMEL_SPI_CSRx_DLYBCT(x)	((x) << 24)