ARM: socfpga: Fix socfpga compilation with early_printk() enabled

This fixes early_printk() compilation for
socfpga. (senduart/busyuart/waituart were missing). It does that by
making Picochip code generic.

Signed-off-by: Pavel Machek <pavel@denx.de>
Acked-by: Dinh Nguyen <dinguyen@altera.com>
Acked-by: Jamie Iles <jamie@jamieiles.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>