The rkisp1 and rpi pipeline handlers duplicate code to handle the
LIBCAMERA_RKISP1_TUNING_FILE and LIBCAMERA_RPI_TUNING_FILE environment
variables that override tuning file selection. Move the common code to
IPAProxy::configurationFile() to avoid the duplication, and make the
feature available to all pipeline handlers with the same behaviour.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Stefan Klug <stefan.klug@ideasonboard.com>