ath10k: pass cal data location as an argument to ath10k_download_cal_{file|dt}

Both ath10k_download_cal_file() and ath10k_download_cal_dt() uses
hard coded file pointer (ar->cal_file) and device tree entry
(qcom,ath10k-calibration-data) respectively to get calibration
data content.

There is a need to use those two functions in qca4019 calibration
download sequence with different file pointer and device tree entry name.
Modify those two functions to take cal data location as an argument.
So that it can serve the purpose for other file pointer and device
tree entry.

This is just preparation before adding actual qca4019 calibration
download sequence. No functional changes.

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