gdsys: mpc8308: Use shadow register for output GPIO values

Since the gpio output status on MPC8xxx cannot be read back, it has to
be buffered locally.

Signed-off-by: Dirk Eibach <dirk.eibach@gdsys.cc>
Signed-off-by: Mario Six <mario.six@gdsys.cc>
diff --git a/board/gdsys/mpc8308/hrcon.c b/board/gdsys/mpc8308/hrcon.c
index 79e3b25..d14a28e 100644
--- a/board/gdsys/mpc8308/hrcon.c
+++ b/board/gdsys/mpc8308/hrcon.c
@@ -287,8 +287,8 @@
 	/*
 	 * set "startup-finished"-gpios
 	 */
-	setbits_be32(&immr->gpio[0].dir, (BIT(31 - 11) | BIT(31 - 12)));
-	setbits_be32(&immr->gpio[0].dat, BIT(31 - 12));
+	setbits_be32(&immr->gpio[0].dir, BIT(31 - 11) | BIT(31 - 12));
+	setbits_gpio0_out(BIT(31 - 12));
 }
 
 int mpc8308_get_fpga_done(uint fpga)