drm/bridge: panel: convert to devm_drm_bridge_alloc() API

drm/bridge: panel: convert to devm_drm_bridge_alloc() API

This is the new API for allocating DRM bridges.

The devm lifetime management of this driver is peculiar. The underlying
device for the panel_bridge is the panel, and the devm lifetime is tied the
panel device (panel->dev). However the panel_bridge allocation is not
performed by the panel driver, but rather by a separate entity (typically
the previous bridge in the encoder chain).

Thus when that separate entity is destroyed, the panel_bridge is not
removed automatically by devm, so it is rather done explicitly by calling
drm_panel_bridge_remove(). This is the function that does devm_kfree() the
panel_bridge in current code, so update it as well to put the bridge
reference instead.

This is a temporary solution until the panel lifetime is reworked, which
should make this workaround unnecessary, so add a comment to clarify that.

Acked-by: Maxime Ripard <mripard@kernel.org>
Link: https://lore.kernel.org/r/20250509-drm-bridge-convert-to-alloc-api-v3-21-b8bc1f16d7aa@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>