spi: designware_spi: Use GENMASK

Replace numeric mask hexcodes with GENMASK macro
in designware_spi

Cc: Stefan Roese <sr@denx.de>
Cc: Marek Vasut <marex@denx.de>
Reviewed-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Jagan Teki <jteki@openedev.com>

drivers/spi/designware_spi.c

@@ -74,7 +74,7 @@ DECLARE_GLOBAL_DATA_PTR;
 #define SPI_CFS_OFFSET			12
 
 /* Bit fields in SR, 7 bits */
-#define SR_MASK				0x7f		/* cover 7 bits */
+#define SR_MASK				GENMASK(6, 0)	/* cover 7 bits */
 #define SR_BUSY				BIT(0)
 #define SR_TF_NOT_FULL			BIT(1)
 #define SR_TF_EMPT			BIT(2)