rsi: update autorate request command frame

When Short Gaurd Interval is enabled bit 9 is set in rate. Otherwise
it should not be set. Added missing 'else' case in this patch.

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>