ath10k: drop MPDU which has discard flag set by firmware for SDIO

When the discard flag is set by the firmware for an MPDU, it should be
dropped. This allows a mitigation for CVE-2020-24588 to be implemented
in the firmware.

Tested-on: QCA6174 hw3.2 SDIO WLAN.RMH.4.4.1-00049

Cc: stable@vger.kernel.org
Signed-off-by: Wen Gong <wgong@codeaurora.org>
Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
Link: https://lore.kernel.org/r/20210511200110.11968c725b5c.Idd166365ebea2771c0c0a38c78b5060750f90e17@changeid


Signed-off-by: Johannes Berg <johannes.berg@intel.com>