android: Introduce CameraBuffer interface

In order to provide support for different memory backends,
move the MappedCamera3Buffer class definition outside of the
CameraDevice class to its own file and rename it in CameraBuffer.

The interface defined in camera_buffer.h will be implemented by
different backends that will be placed in the src/android/mm
subdirectory.

Provide a first implementation for the 'generic android' backend
which matches the existing one.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>

src/android/camera_device.h

@@ -24,17 +24,12 @@
 #include "libcamera/internal/log.h"
 #include "libcamera/internal/message.h"
 
+#include "camera_buffer.h"
 #include "camera_metadata.h"
 #include "camera_stream.h"
 #include "camera_worker.h"
 #include "jpeg/encoder.h"
 
-class MappedCamera3Buffer : public libcamera::MappedBuffer
-{
-public:
-	MappedCamera3Buffer(const buffer_handle_t camera3buffer, int flags);
-};
-
 class CameraDevice : protected libcamera::Loggable
 {
 public: