ipa: ipu3: awb: Add support for color temperature

The AWB estimates the color temperature, but it is not used at all. It
can be useful for debug purpose at least, but also for lux estimation
later, to be able to know the temperature estimated for a given frame.

Add a new member to the IPAFrameContext::awb for this purpose, and
update the value in AWB.

Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Umang Jain <umang.jain@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>

src/ipa/ipu3/ipa_context.cpp

@@ -117,6 +117,9 @@ namespace libcamera::ipa::ipu3 {
  *
  * \var IPAFrameContext::awb.gains.blue
  * \brief White balance gain for B channel
+ *
+ * \var IPAFrameContext::awb.temperatureK
+ * \brief Estimated color temperature
  */
 
 /**