drm: bridge: ti-sn65dsi83: Switch to atomic operations

Use the atomic version of the enable/disable operations to continue the
transition to the atomic API, started with the introduction of
.atomic_get_input_bus_fmts(). This will be needed to access the mode
from the atomic state.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210621125518.13715-4-laurent.pinchart@ideasonboard.com