ath10k: fetch (pre-)calibration data via nvmem subsystem

ATH10K chips are used it wide range of routers,
accesspoints, range extenders, network appliances.
On these embedded devices, calibration data is often
stored on the main system's flash and was out of reach
for the driver.

To bridge this gap, ath10k is getting extended to pull
the (pre-)calibration data through nvmem subsystem.
To do this, a nvmem-cell containing the information can
either be specified in the platform data or via device-tree.

Tested with:
        Netgear EX6150v2 (IPQ4018 - pre-calibration method)
        TP-Link Archer C7 v2 (QCA9880v2 - old calibration method)

Cc: Robert Marko <robimarko@gmail.com>
Cc: Thibaut VARÈNE <hacks@slashdirt.org>
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20211016234609.1568317-1-chunkeey@gmail.com