drm: exynos: dsi: Convert to bridge driver

Convert the encoders to bridge drivers in order to standardize on
a single API with built-in dumb encoder support for compatibility
with existing component drivers.

Driver bridge conversion will help to reuse the same bridge on
different platforms as exynos dsi driver can be used as a Samsung
DSIM and use it for i.MX8MM platform.

Bridge conversion,

- Drops drm_encoder_helper_funcs.

- Adds drm_bridge_funcs and register a drm bridge.

- Drops bridge_chain.

- Separate pre_enable from enable function.

- Separate post_disable from disable function.

Convert it.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220303163654.3381470-6-jagan@amarulasolutions.com