serial: mpc8xx: Move serial registration from serial_initialize()

Move the registration of serial_smc and serial_scc ports from
default serial_initialize() into CPU specific function called from
serial_initialize(). This slims down the serial_initialize() call
to a bare tracker of all possible serial port registration routines
in U-Boot.

The exports of both serial_scc_device and serial_smc_device can
not yet be removed as they are still used in default_serial_console()
calls.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Marek Vasut <marek.vasut@gmail.com>
Cc: Tom Rini <trini@ti.com>
Cc: Anatolij Gustschin <agust@denx.de>
Cc: Stefan Roese <sr@denx.de>
Cc: Mike Frysinger <vapier@gentoo.org>
diff --git a/arch/powerpc/cpu/mpc8xx/serial.c b/arch/powerpc/cpu/mpc8xx/serial.c
index dc9b323..00888e9 100644
--- a/arch/powerpc/cpu/mpc8xx/serial.c
+++ b/arch/powerpc/cpu/mpc8xx/serial.c
@@ -681,6 +681,17 @@
 #endif
 }
 
+void mpc8xx_serial_initialize(void)
+{
+#if defined(CONFIG_8xx_CONS_SMC1) || defined(CONFIG_8xx_CONS_SMC2)
+	serial_register(&serial_smc_device);
+#endif
+#if	defined(CONFIG_8xx_CONS_SCC1) || defined(CONFIG_8xx_CONS_SCC2) || \
+	defined(CONFIG_8xx_CONS_SCC3) || defined(CONFIG_8xx_CONS_SCC4)
+	serial_register(&serial_scc_device);
+#endif
+}
+
 #ifdef CONFIG_MODEM_SUPPORT
 void disable_putc(void)
 {