iwlwifi: mvm: fix setting HE ppe FW config

The FW expects to get the ppe value for each NSS-BW pair in the same
format as in the he phy capabilities IE, which means that a value of 0
implies ppe should be used for BPSK (mcs 0). If there are no PPE
thresholds in the IE, or if for some NSS-RU pair there's no threshold
set for it (this could happen because it's a variable-sized field), it
means no PPE should not be used for that pair, so the value sent to FW
should be 7 which corresponds to "none".

Fixes: 514c30696f ("iwlwifi: add support for IEEE802.11ax")
Signed-off-by: Naftali Goldstein <naftali.goldstein@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/intel/iwlwifi/fw/api/mac.h

@@ -443,7 +443,7 @@ struct iwl_he_backoff_conf {
  * Support for Nss x BW (or RU) matrix:
  *	(0=SISO, 1=MIMO2) x (0-20MHz, 1-40MHz, 2-80MHz, 3-160MHz)
  * Each entry contains 2 QAM thresholds for 8us and 16us:
- *	0=BPSK, 1=QPSK, 2=16QAM, 3=64QAM, 4=256QAM, 5=1024QAM, 6/7=RES
+ *	0=BPSK, 1=QPSK, 2=16QAM, 3=64QAM, 4=256QAM, 5=1024QAM, 6=RES, 7=NONE
  * i.e. QAM_th1 < QAM_th2 such if TX uses QAM_tx:
  *	QAM_tx < QAM_th1            --> PPE=0us
  *	QAM_th1 <= QAM_tx < QAM_th2 --> PPE=8us