sunxi: Select CONFIG_OF_BOARD_SETUP from arch/arm/Kconfig

Always select OF_BOARD_SETUP on sunxi, rather then having it in almost
all our defconfigs. This also fixes it missing from some recently
added defconfigs.

This commit also modifies our ft_board_setup() to not cause warnings
when CONFIG_VIDEO_DT_SIMPLEFB is not set, since we will now always
build it.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>