Sync SiByte system code to the new DUART driver

["Imre Kaloz" <kaloz@openwrt.org>]

The new upstream SiByte DUART driver uses a different config option then
the old one, so the SiByte target doesn't compile currently.
This patch fixes the problem.

Signed-off-by: Imre Kaloz <kaloz@openwrt.org>

---

diff --git a/arch/mips/sibyte/cfe/console.c b/arch/mips/sibyte/cfe/console.c
index c6ec748..4cec9d7 100644
--- a/arch/mips/sibyte/cfe/console.c
+++ b/arch/mips/sibyte/cfe/console.c
@@ -46,7 +46,7 @@ static int cfe_console_setup(struct console *cons, char *str)
        /* XXXKW think about interaction with 'console=' cmdline arg */
        /* If none of the console options are configured, the build will break. 
*/
        if (cfe_getenv("BOOT_CONSOLE", consdev, 32) >= 0) {
-#ifdef CONFIG_SIBYTE_SB1250_DUART
+#ifdef CONFIG_SERIAL_SB1250_DUART
                if (!strcmp(consdev, "uart0")) {
                        setleds("u0cn");
                } else if (!strcmp(consdev, "uart1")) {