serial: pxa: Make use of default_serial_console in serial_pxa

Make use of the newly implemented weak default_serial_console in
the serial_pxa driver. This removes all reimplementations of this
function from board files.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Marek Vasut <marek.vasut@gmail.com>
Cc: Tom Rini <trini@ti.com>
diff --git a/include/configs/vpac270.h b/include/configs/vpac270.h
index 424a902..5e948f94a 100644
--- a/include/configs/vpac270.h
+++ b/include/configs/vpac270.h
@@ -75,6 +75,7 @@
  */
 #define	CONFIG_PXA_SERIAL
 #define	CONFIG_FFUART			1
+#define CONFIG_CONS_INDEX		3
 #define	CONFIG_BAUDRATE			115200
 
 /*