drm/mipi-dsi: Create devm device attachment

MIPI-DSI devices need to call mipi_dsi_attach() when their probe is done
to attach against their host.

However, at removal or when an error occurs, that attachment needs to be
undone through a call to mipi_dsi_detach().

Let's create a device-managed variant of the attachment function that
will automatically detach the device at unbind.

Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20210910101218.1632297-5-maxime@cerno.tech