drm/tilcdc: Configure video mode to HW in enable() not in mode_set_nofb()

Configure video mode to HW in enable() call back. There is no reason
to do it before that. This makes PM functions way easier because there
is no HW context to save when screen is for instance blanked. This
patch removes mode_set_nofb() call back from tilcdc.

Signed-off-by: Jyri Sarha <jsarha@ti.com>
Tested-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>