rsi: update tx auto rate command frame for AP mode

Auto rate frame is sent to firmware when a new station is
connected. Station id and station's ht capabilities are updated
in auto rate command frame.

Signed-off-by: Prameela Rani Garnepudi <prameela.j04cs@gmail.com>
Signed-off-by: Amitkumar Karwar <amit.karwar@redpinesignals.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>