dt: bindings: net: add bindings of WCN6750 for ath11k

WCN6750 is the WLAN chip on Qualcomm Snapdragon SoC SC7280;
Though being a PCIe based solution, it is not attached to
the APSS processor (Application Processor SubSystem), it is
instead attached to another tiny processor called WPSS Q6
processor (Wireless Processor SubSystem) on the SC7280 MSM,
where the WLAN firmware runs, and it is the WLAN firmware
running on the Q6 processor which enumerates WCN6750, as a
result APPS processor would never know such a device being
present in the system and would not detect the WCN6750
hardware unless and otherwise WCN6750 is registered as a
platform device. This is the reason behind adding WCN6750
WLAN node in the device tree.

Add WCN6750 wireless driver support, its based on ath11k driver.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Manikanta Pubbisetty <quic_mpubbise@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20220429170502.20080-2-quic_mpubbise@quicinc.com