ipa: Add start() and stop() operations

Add two new operations to the IPA interface to start and stop it. The
intention is that these functions shall be used by the IPA to perform
actions when the camera is started and stopped.

Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

src/libcamera/proxy/ipa_proxy_linux.cpp

@@ -27,6 +27,8 @@ public:
 	~IPAProxyLinux();
 
 	int init() override { return 0; }
+	int start() override { return 0; }
+	void stop() override {}
 	void configure(const std::map<unsigned int, IPAStream> &streamConfig,
 		       const std::map<unsigned int, const ControlInfoMap &> &entityControls) override {}
 	void mapBuffers(const std::vector<IPABuffer> &buffers) override {}