ath11k: Update tx and rx chain count properly on drv_set_antenna

Set the number of tx and rx chains properly on drv_set_antenna().
This will ensure the related ht/vht/he caps are properly recalculated
based on the tx/rx chains set.

Signed-off-by: Sriram R <srirrama@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>