Fix AX HE capability advertisement

[DurkaEbanaya]

PR Body

Summary

This PR fixes AX/HE capability advertisement for Intel iwx devices and hardens HE IE handling.

Main changes:

• Enable IEEE80211_F_HEON when setting up iwx HE rates/capabilities.
• Advertise HE 5 GHz channel width support for 40/80 MHz and 160 MHz in phy_cap_info[0].
• When selecting 11AX media mode, keep HT and VHT enabled together with HE so the association request advertises normal HT/VHT/HE capabilities instead of HE only.
• Fix HE rate table values used for 11AX status/rate reporting and add 11AX handling in ItlNetworkUserClient.
• Fix HE Capabilities IE length handling when PPE Threshold is absent.
• Avoid HE Capabilities PPE parsing overread and add a short-length guard for HE Operation parsing.
• Avoid copying beyond the local PPE threshold initializer.

Why

On a 160 MHz-capable AX setup, the driver built an HE Capabilities IE but did not advertise the 5 GHz HE channel width bits in phy_cap_info[0].

In testing, that caused reverse/downlink throughput around ~130 Mbit/s, with RX PHY reporting VHT at only 20 MHz. After advertising the correct HE 5 GHz width capabilities and keeping the normal VHT+HE association path, the same setup negotiated stable wide-channel operation.

This PR intentionally does not force HE-only association or remove VHT capabilities. The client advertises its VHT and HE capabilities and leaves the final VHT/HE downlink decision to the AP/firmware.

Testing

Built successfully:

xcodebuild -project itlwm.xcodeproj -scheme itlwm -configuration Debug build
LAN iperf3 tests after reboot:

iperf3 -c 192.168.1.42 -R -t 60 -O 5: 568 Mbit/s, 6 retransmits
iperf3 -c 192.168.1.42 -t 60 -O 5: 471 Mbit/s
iperf3 -c 192.168.1.42 -R -P 4 -t 60 -O 5: 647 Mbit/s aggregate
iperf3 -c 192.168.1.42 -P 4 -t 60 -O 5: 474 Mbit/s aggregate, 0 retransmits
Compared with the pre-fix behavior, reverse/downlink throughput improved from ~130 Mbit/s to stable wide-channel performance, without forcing HE-only operation.