ARM: sunxi: Use the Synosys APB UART instead of ns8250

The UART controller used in the A10/A13 is the Synopsys DesignWare 8250.
The wrong use of a regular 8250 driver may lead to a oops during kernel
boot with "irq 17: nobody cared", because the apb UART as an extra
interrupt that gets raised when writing to the LCR when busy.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>