wifi: mac80211: fix memory leak in ieee80211_register_hw()

In the Linux kernel, the following vulnerability has been resolved: wifi: mac80211: fix memory leak in ieee80211_register_hw() If kmemdup() fails while copying supported band structures, the error path jumps to fail_rate. This skips rate_control_deinitialize() and leaks the initialized local->rate_ctrl. Fix this by adding a fail_band label that shares the rate-control cleanup path before falling through to the remaining teardown. The bug was first flagged by an experimental analysis tool we are developing for kernel memory-management bugs while analyzing v6.13-rc1. The tool is still under development and is not yet publicly available. Manual inspection confirms that the bug is still present in v7.1-rc7. An x86_64 allyesconfig build showed no new warnings. As we do not have a suitable mac80211 device/driver combination to test with, no runtime testing was able to be performed.