serial: s5p: Move serial registration from serial_initialize()

Move the registration of s5p_serialN_device ports from default
serial_initialize() into driver 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 newly implemented s5p_serial_initialize() function, which is
implemented inside of the serial_s5p driver allows encapsulation
of s5p_serialN_device within the serial_s5p driver itself.

Also, remove the exports of s5p_serialN_device from include/serial.h
as they are no longer needed. This is simply because the implementation of
default_serial_console() is wrapped into the serial_s5p driver and
the default console is picked by CONFIG_SERIAL<N> macro in config file.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Marek Vasut <marek.vasut@gmail.com>
Cc: Tom Rini <trini@ti.com>
Cc: Minkyu Kang <mk7.kang@samsung.com>
diff --git a/common/serial.c b/common/serial.c
index 70f6261..bed907e 100644
--- a/common/serial.c
+++ b/common/serial.c
@@ -43,6 +43,7 @@
 serial_initfunc(mpc8xx_serial_initialize);
 serial_initfunc(pxa_serial_initialize);
 serial_initfunc(s3c24xx_serial_initialize);
+serial_initfunc(s5p_serial_initialize);
 
 void serial_register(struct serial_device *dev)
 {
@@ -78,12 +79,7 @@
 #endif /* CONFIG_SYS_NS16550_SERIAL */
 	pxa_serial_initialize();
 	s3c24xx_serial_initialize();
-#if defined(CONFIG_S5P)
-	serial_register(&s5p_serial0_device);
-	serial_register(&s5p_serial1_device);
-	serial_register(&s5p_serial2_device);
-	serial_register(&s5p_serial3_device);
-#endif
+	s5p_serial_initialize();
 #if defined(CONFIG_MPC512X)
 #if defined(CONFIG_SYS_PSC1)
 	serial_register(&serial1_device);