drm/bridge: lt9611uxc: Switch to devm MIPI-DSI helpers

[ Upstream commit 293ada7b ]

Let's switch to the new devm MIPI-DSI function to register and attach
our secondary device.

Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20211025151536.1048186-10-maxime@cerno.tech


Stable-dep-of: 15fe53be ("drm/bridge: lt9611uxc: fix the race in the error path")
Signed-off-by: Sasha Levin <sashal@kernel.org>