fbdev: da8xx-fb: drop a redundant if

The driver data is always set in probe. The remove() callback won't be
called if probe failed which is the only way for it to be NULL. Remove
the redundant if.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>