ipa: raspberrypi: Return an error code from Algorithm::read()

When encountering errors, the Algorithm::read() function either uses
LOG(Fatal) or throws exceptions from the boost property_tree functions.
To prepare for replacing boost JSON parse with the YamlParser class,
give the Algorithm::read() function the ability to return an error code,
and propagate it all the way to the IPA module init() function.

All algorithm classes return a hardcoded 0 value for now, subsequent
commits will change that.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Naushir Patuck <naush@raspberrypi.com>
Tested-by: Naushir Patuck <naush@raspberrypi.com>

src/ipa/raspberrypi/controller/algorithm.cpp

@@ -9,8 +9,9 @@
 
 using namespace RPiController;
 
-void Algorithm::read([[maybe_unused]] boost::property_tree::ptree const &params)
+int Algorithm::read([[maybe_unused]] boost::property_tree::ptree const &params)
 {
+	return 0;
 }
 
 void Algorithm::initialise()