drm/omap: remove unused header tcm-sita.h

tcm-sita.h is unused since commit 0d6fa53f ("drm/omap: Use bitmaps for TILER placement")
Let's remove it.

Signed-off-by: Corentin Labbe <clabbe@baylibre.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>