ath10k: read calibration data from Device Tree

This patch adds support for reading calibration data from Device Tree.
It looks for the calibration data in Device Tree if it can't find it
in a file. If there's no node in Device Tree, ath10k will try to find the
calibration data from OTP.

The node for the calibration data should be defined like this:

pci {
        pcie@0 {
                reg = <0 0 0 0 0>;
                #interrupt-cells = <1>;
                #size-cells = <2>;
                #address-cells = <3>;
                device_type = "pci";

                ath10k@0,0 {
                        reg = <0 0 0 0 0>;
                        device_type = "pci";
                        qcom,ath10k-calibration-data = [ 01 02 03 ... ];
                };
        };
};

Signed-off-by: Toshi Kikuchi <toshik@chromium.org>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>