wifi: ath6kl: fix OOB read from firmware num_msg in TX complete handler

In the Linux kernel, the following vulnerability has been resolved: wifi: ath6kl: fix OOB read from firmware num_msg in TX complete handler The firmware-controlled num_msg field (u8, 0-255) drives the loop in ath6kl_wmi_tx_complete_event_rx() without validation against the buffer length. This allows out-of-bounds reads of up to 1020 bytes past the WMI event buffer when the firmware sends an inflated num_msg. Add a check that the buffer is large enough to hold the fixed struct and the num_msg variable-length entries.