drm/exynos: do not start enabling DP at bind() phase

The DP device will be properly enabled at the enable() call just
after the bind call finishes.

Changelog v2:
- no change

Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Signed-off-by: Inki Dae <inki.dae@samsung.com>