libcamera: timer: Add start() method with absolute deadline

The Timer class is started using a timer duration. To help callers that
require waiting for an absolute deadline, add a start() overload that
takes a std::chrono::steady_clock::time_point value. This will be used
by IPAs.

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

include/libcamera/timer.h

@@ -25,6 +25,7 @@ public:
 
 	void start(unsigned int msec) { start(std::chrono::milliseconds(msec)); }
 	void start(std::chrono::milliseconds duration);
+	void start(std::chrono::steady_clock::time_point deadline);
 	void stop();
 	bool isRunning() const;