m68k: Rename CONFIG_WATCHDOG_TIMEOUT to CONFIG_WATCHDOG_TIMEOUT_MSECS

In practice, it is clear that the usage in m68k of
CONFIG_WATCHDOG_TIMEOUT is setting a value in milliseconds. Rename this
to the existing symbol and move to Kconfig.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/arch/m68k/cpu/mcf523x/cpu.c b/arch/m68k/cpu/mcf523x/cpu.c
index 6d87908..ba2c228 100644
--- a/arch/m68k/cpu/mcf523x/cpu.c
+++ b/arch/m68k/cpu/mcf523x/cpu.c
@@ -92,7 +92,7 @@
 	u32 wdog_module = 0;
 
 	/* set timeout and enable watchdog */
-	wdog_module = ((CFG_SYS_CLK / CONFIG_SYS_HZ) * CONFIG_WATCHDOG_TIMEOUT);
+	wdog_module = ((CFG_SYS_CLK / CONFIG_SYS_HZ) * CONFIG_WATCHDOG_TIMEOUT_MSECS);
 	wdog_module |= (wdog_module / 8192);
 	out_be16(&wdp->mr, wdog_module);