ath11k: extend peer_assoc_cmd for 6GHz band

This adds support required for configuring min_data_rate of 6GHz oper IE
and peer_he_caps_6ghz in peer assoc command. The Minimum Rate field
indicates the minimum rate, in units of 1 Mb/s, that the non-AP STA is
allowed to use for sending PPDUs as defined in IEEE P802.11ax™/D6.0.

Signed-off-by: Pradeep Kumar Chitrapu <pradeepc@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200603001724.12161-5-pradeepc@codeaurora.org