kernel: wifi: ath11k: decrease MHI channel buffer length to 8KB

In the Linux kernel, the following vulnerability has been resolved: wifi: ath11k: decrease MHI channel buffer length to 8KB The Linux kernel CVE team has assigned CVE-2024-35938 to this issue. Upstream advisory: https://lore.kernel.org/linux-cve-announce/2024051918-CVE-2024-35938-0100@gregkh/T...