dt: bindings: ath10k: add dt entry for XO calibration support

Add dt binding to get xo calibration data support for wifi rf clock.

Signed-off-by: Govind Singh <govinds@codeaurora.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>