ath10k: add cycle/rx_clear counters frequency to hw_params

The frequency at which cycle/rx_clear counters are running might
change from one target type to another. QCA99X0 is running the
counters at 150Mhz while QCA9888X and QCA6174 are running at 88Mhz.
Add a new entry to hw_params to store the target specific frequency
and use it in msecs conversion. This change fixes inconsistent
channel active/busy time.

Signed-off-by: Vasanthakumar Thiagarajan <vthiagar@qti.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>