iwlwifi: pcie: make sure iwl_rx_packet_payload_len() will not underflow

iwlwifi: pcie: make sure iwl_rx_packet_payload_len() will not underflow

If the device is malfunctioning and reports too short rx descriptor
length, iwl_rx_packet_payload_len() will underflow, eventually resulting
in accessing memory out of bounds and other bad things. Prevent this.

Signed-off-by: Andrei Otcheretianski <andrei.otcheretianski@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20220130115024.ea00b52c6f25.I8b79b14f1af8b6f2f579f97b397b9e005fe446b1@changeid
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>