sparc: leon3: Clear GD_FLAG_SERIAL_READY flag on AMBA failure

Clear the GD_FLG_SERIAL_READY flag on AMBA P&P lookup failure so that the
panic function can use DEBUG_UART driver. drivers/serial/serial.c set this
flag before calling this function, preventing DEBUG_UART code from running.

Signed-off-by: Francois Retief <fgretief@spaceteq.co.za>

arch/sparc/cpu/leon3/serial.c

@@ -29,6 +29,7 @@ static int leon3_serial_init(void)
 	/* find UART */
 	if (ambapp_apb_find(&ambapp_plb, VENDOR_GAISLER, GAISLER_APBUART,
 		CONFIG_SYS_GRLIB_APBUART_INDEX, &apbdev) != 1) {
+		gd->flags &= ~GD_FLG_SERIAL_READY;
 		panic("%s: apbuart not found!\n", __func__);
 		return -1; /* didn't find hardware */
 	}