CVE-2025-68738 wifi: mt76: mt7996: fix null pointer deref in mt7996_conf_tx()

In the Linux kernel, the following vulnerability has been resolved: wifi: mt76: mt7996: fix null pointer deref in mt7996conftx If a link does not have an assigned channel yet, mt7996viflink returns NULL. We still need to store the updated queue settings in that case, and apply them later. Move th...