wcn36xx: initialize device defaults on start

Set up default configuration for the device when we call start.
The defaults come from dumps from the prima driver for the same
hardware.

This fixes transmit A-MPDU; previously only one MPDU would be
sent per A-MPDU due to missing MAX_MPDUS_IN_AMPDU setting.

Signed-off-by: Bob Copeland <me@bobcopeland.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>