sunxi: Add support for UART0 in PB pin group on A33

The A33 adds a pinmux function for UART0 in the PB pin group.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>