ARM: davinci: da850: fix selecting ARCH_DAVINCI_DA8XX

Chips in the DA850 family need to have ARCH_DAVINCI_DA8XX to be selected
in order to enable some peripheral drivers.

This was accidentally removed in a previous commit.

Fixes: dec85a95 ("ARM: davinci: clean up platform support")
Signed-off-by: David Lechner <dlechner@baylibre.com>
Acked-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>