ARM: davinci: move timer definitions to davinci.h

Boards from the dm* family rely on register offset definitions from
arch/arm/mach-davinci/include/mach/time.h. We'll be removing this file
soon, so move the required defines to davinci.h where the rest of such
constants live.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Reviewed-by: David Lechner <david@lechnology.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>