watchdog: imx7ulp: Use definitions instead of magic values

Use definitions instead of magic values in order to improve readability.

Since the CLK field of the WDOG CS register is composed of two bits
to select the watchdog clock source, use a shift representation
instead of BIT().
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20191029174037.25381-5-festevam@gmail.comSigned-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

drivers/watchdog/imx7ulp_wdt.c

@@ -17,6 +17,9 @@
 #define WDOG_CS_CMD32EN		BIT(13)
 #define WDOG_CS_ULK		BIT(11)
 #define WDOG_CS_RCS		BIT(10)
+#define LPO_CLK			0x1
+#define LPO_CLK_SHIFT		8
+#define WDOG_CS_CLK		(LPO_CLK << LPO_CLK_SHIFT)
 #define WDOG_CS_EN		BIT(7)
 #define WDOG_CS_UPDATE		BIT(5)
 
@@ -129,7 +132,7 @@ static void imx7ulp_wdt_init(void __iomem *base, unsigned int timeout)
 	/* set an initial timeout value in TOVAL */
 	writel(timeout, base + WDOG_TOVAL);
 	/* enable 32bit command sequence and reconfigure */
-	val = BIT(13) | BIT(8) | BIT(5);
+	val = WDOG_CS_CMD32EN | WDOG_CS_CLK | WDOG_CS_UPDATE;
 	writel(val, base + WDOG_CS);
 }