ipa: raspberrypi: awb: Update colour temperature whenever manual gains change

Previously we only did this when the system starts (on the first
switch_mode). Now we do it whenever the manual colour gains are
updated. To facilitate this, this R/B vs. colour temperature inverse
functions are stored persistently in the AwbConfig.

Signed-off-by: David Plowman <david.plowman@raspberrypi.com>
Reviewed-by: Naushir Patuck <naush@raspberrypi.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/ipa/raspberrypi/controller/rpi/awb.h

@@ -42,6 +42,8 @@ struct AwbConfig {
 	bool fast; /* "fast" mode uses a 16x16 rather than 32x32 grid */
 	Pwl ctR; /* function maps CT to r (= R/G) */
 	Pwl ctB; /* function maps CT to b (= B/G) */
+	Pwl ctRInverse; /* inverse of ctR */
+	Pwl ctBInverse; /* inverse of ctB */
 	/* table of illuminant priors at different lux levels */
 	std::vector<AwbPrior> priors;
 	/* AWB "modes" (determines the search range) */
@@ -168,7 +170,6 @@ private:
 	double manualR_;
 	/* manual b setting */
 	double manualB_;
-	bool firstSwitchMode_; /* is this the first call to SwitchMode? */
 };
 
 static inline Awb::RGB operator+(Awb::RGB const &a, Awb::RGB const &b)