drm: zynqmp_dp: convert to devm_drm_bridge_alloc() API

drm: zynqmp_dp: convert to devm_drm_bridge_alloc() API

This is the new API for allocating DRM bridges.

This driver has a peculiar structure. zynqmp_dpsub.c is the actual driver,
which delegates to a submodule (zynqmp_dp.c) the allocation of a
sub-structure embedding the drm_bridge and its initialization, however it
does not delegate the drm_bridge_add(). Hence, following carefully the code
flow, it is correct to change the allocation function and .funcs assignment
in the submodule, while the drm_bridge_add() is not in that submodule.

Acked-by: Maxime Ripard <mripard@kernel.org>
Link: https://lore.kernel.org/r/20250509-drm-bridge-convert-to-alloc-api-v3-17-b8bc1f16d7aa@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>