serial: pxa: Move serial registration from serial_initialize()

Move the registration of serial_XXuart 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 pxa_serial_initialize() function, which is
implemented inside of the serial_pxa driver allows encapsulation
of serial_XXuart within the serial_pxa driver itself.

Also, remove the exports of serial_XXuart 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_pxa driver and
the default console is picked by CONFIG_CONS_IDX 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>
diff --git a/common/serial.c b/common/serial.c
index 9e88f97..70f6261 100644
--- a/common/serial.c
+++ b/common/serial.c
@@ -41,6 +41,7 @@
 		__attribute__((weak, alias("serial_null")));
 
 serial_initfunc(mpc8xx_serial_initialize);
+serial_initfunc(pxa_serial_initialize);
 serial_initfunc(s3c24xx_serial_initialize);
 
 void serial_register(struct serial_device *dev)
@@ -75,15 +76,7 @@
 	serial_register(&eserial4_device);
 #endif
 #endif /* CONFIG_SYS_NS16550_SERIAL */
-#if defined(CONFIG_FFUART)
-	serial_register(&serial_ffuart_device);
-#endif
-#if defined(CONFIG_BTUART)
-	serial_register(&serial_btuart_device);
-#endif
-#if defined(CONFIG_STUART)
-	serial_register(&serial_stuart_device);
-#endif
+	pxa_serial_initialize();
 	s3c24xx_serial_initialize();
 #if defined(CONFIG_S5P)
 	serial_register(&s5p_serial0_device);