drm/i915/panel: register drm_panel and call prepare/unprepare for eDP

Allocate and register drm_panel to allow the panel_follower framework to
detect the eDP panel and pass drm_connector::kdev device to drm_panel
allocation for matching.
Call drm_panel_prepare/unprepare in ddi_enable for eDP to allow the
followers to get notified of the panel power state changes.

Note: This is for eDP with DDI platforms only.

v2: remove backlight setup from panel_register (Jani)
v3: Updated the commit message (Jani)

Signed-off-by: Arun R Murthy <[e-mail]>
Reviewed-by: Jani Nikula <[e-mail]>
Signed-off-by: Suraj Kandpal <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/gpu/drm/i915/display/intel_ddi.c

···
 #include "intel_lspcon.h"
 #include "intel_mg_phy_regs.h"
 #include "intel_modeset_lock.h"
+#include "intel_panel.h"
 #include "intel_pfit.h"
 #include "intel_pps.h"
 #include "intel_psr.h"
···
 	drm_connector_update_privacy_screen(conn_state);
 	intel_edp_backlight_on(crtc_state, conn_state);
 
+	intel_panel_prepare(crtc_state, conn_state);
+
 	if (!intel_lspcon_active(dig_port) || intel_dp_has_hdmi_sink(&dig_port->dp))
 		intel_dp_set_infoframes(encoder, true, crtc_state, conn_state);
 
···
 
 	intel_dp->link.active = false;
 
+	intel_panel_unprepare(old_conn_state);
 	intel_psr_disable(intel_dp, old_crtc_state);
 	intel_alpm_disable(intel_dp);
 	intel_edp_backlight_off(old_conn_state);

drivers/gpu/drm/i915/display/intel_panel.c

···
 	if (ret)
 		return ret;
 
-	if (connector->base.connector_type == DRM_MODE_CONNECTOR_DSI) {
+	if (connector->base.connector_type == DRM_MODE_CONNECTOR_DSI ||
+	    connector->base.connector_type == DRM_MODE_CONNECTOR_eDP) {
 		struct device *dev = connector->base.kdev;
 		struct drm_panel *base;