drm/i915: Introduce intel_panel_init_alloc()

[ Upstream commit f70f8153

 ]

Introduce a place where we can initialize connector->panel
after it's been allocated. We already have a intel_panel_init()
so had to get creative with the name and came up with
intel_panel_init_alloc().

Cc: Animesh Manna <animesh.manna@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221125173156.31689-2-ville.syrjala@linux.intel.com
Stable-dep-of: 14e591a1

 ("drm/i915: Populate encoder->devdata for DSI on icl+")
Signed-off-by: Sasha Levin <sashal@kernel.org>