linux-firmware: Transmission of data encrypted with an all-zero session key after disassociation

An issue was discovered on Broadcom Wi-Fi client devices. Specifically timed and handcrafted traffic can cause internal errors (related to state transitions) in a WLAN device that lead to improper layer 2 Wi-Fi encryption with a consequent possibility of information disclosure over the air for a discrete set of traffic, a different vulnerability than CVE-2019-9500, CVE-2019-9501, CVE-2019-9502, and CVE-2019-9503.