ipq806x: chromium: Pull OnHub caldata directly from VPD

ipq806x: chromium: Pull OnHub caldata directly from VPD

The OnHub bootloader tries to patch the calibration directly into the
device tree, but it uses constant paths that look like this:

  static const char *dt_path = "soc/pci@%8.8x/pcie@0/ath10k@0,0";

  https://chromium.googlesource.com/chromiumos/platform/depthcharge/+/refs/heads/firmware-storm-6315.B/src/board/storm/wifi_calibration.c#69

These paths have changed in recent kernels, so we need to adapte.

The CONFIG_GOOGLE_VPD kernel module (provided by kmod-google-firmware)
is present on OnHub, and provides alternative means to locate this
information, in /sys/firmware/vpd/ro/wifi_base64_calibration{0,1,2}. Use
that instead.

Signed-off-by: Brian Norris <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/20477
Signed-off-by: Robert Marko <[email protected]>