ARM: davinci: remove legacy timer support

All platforms have now been switched to the new clocksource driver.
Remove the old code and various no longer needed bits and pieces.

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