drm/exynos: Remove dpms link between encoder/connector

This patch removes the call from encoder dpms into connector dpms (which
will then call back into encoder dpms through the helper function). The
callback is likely to keep connector->dpms in the right state when
initiating dpms from crtc or encoder, but this isn't the right way to do
it. This patch is the first step towards rationalizing power management
in the exynos drm driver.

Signed-off-by: Sean Paul <seanpaul@chromium.org>
Reviewed-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>