ath10k: add recalc RTS/CTS protection method

Add recalculation of RTS/CTS protection when one or more legacy
stations are connected to ath10k. In this case enable RTS/CTS
protection and set sw retry profile are needed in the FW.
Without this change legacy station is starved and has very low
throughput.

Signed-off-by: Marek Kwaczynski <marek.kwaczynski@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>