ath10k: set max spatial stream to 4 for 10.4 fw

10.4 fw supports upto 4 spatial stream. Limit max spatial
stream to 4 for 10.4 firmware and to 3 for non 10.4 firmware.

Signed-off-by: Raja Mani <rmani@qti.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>