arm: davinci: remove unused defines

The last usage of the DV_TIMER_ and DV_WDT_ definitions were removed in
commits 8d775763 ("ARM: davinci: remove support for cam_enc_4xx")
and cef443c1 ("arm: davinci: remove leftover code for dm* SoCs"),
respectively.

Signed-off-by: Emil Kronborg <emil.kronborg@protonmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>