exynos: drm: dsi: Attach in_bridge in MIC driver

MIC drivers in the Exynos5433 display pipeline are already registered
as bridge drivers and it is more advisable to attach the downstream
bridge on the bridge attach call instead of doing the same in the
DSI driver.

This makes bridge attachment more meaningful and avoids the races
during bridge function calls.

So, move the bridge finding and drm_bridge_attach from DSI to MIC.

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/20220303163654.3381470-4-jagan@amarulasolutions.com