drm/exynos: dsi: remove unnecessary pm interfaces

Exynos drm driver is a single driver so pm operation
for kms drivers should be done by connector->dpms
at top level driver.

If kms driver has its own pm interfaces, single driver model
would be broken so this patch removes unnecessary pm interfaces
from dsi driver.

Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>

diff --cc drivers/gpu/drm/exynos/exynos_drm_dsi.c
Simple merge