This got accidentally dropped in the fixed commit and is required for
the driver to properly work on the rev1 IP, such as found on the LCDK.

Fixes: 2b2080d7 ("drm/tilcdc: Get rid of complex ping-pong mechanism")
Signed-off-by: Karl Beldan <kbeldan@baylibre.com>
Signed-off-by: Jyri Sarha <jsarha@ti.com>