drm/bridge: imx8qxp-pixel-combiner: Fix bailout for imx8qxp_pc_bridge_probe()

drm/bridge: imx8qxp-pixel-combiner: Fix bailout for imx8qxp_pc_bridge_probe()

In case the channel0 is unavailable and bailing out from free_child is
needed when we fail to add a DRM bridge for the available channel1,
pointer pc->ch[0] in the bailout path would be NULL and it would be
dereferenced as pc->ch[0]->bridge.next_bridge.  Fix this by checking
pc->ch[0] before dereferencing it.

Fixes: ae754f049ce1 ("drm/bridge: imx8qxp-pixel-combiner: get/put the next bridge")
Fixes: 99764593528f ("drm/bridge: imx8qxp-pixel-combiner: convert to devm_drm_bridge_alloc() API")
Signed-off-by: Liu Ying <victor.liu@nxp.com>
Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20260123-imx8qxp-drm-bridge-fixes-v1-3-8bb85ada5866@nxp.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>