aes2501: set partial flag on an image

Set partial flag to remove false minutiae at the perimeter of a scan

libfprint/drivers/aes2501.c

@@ -505,6 +505,7 @@ static void capture_read_strip_cb(struct libusb_transfer *transfer)
 			}
 			img = fpi_assemble_frames(&assembling_ctx,
 						  aesdev->strips, aesdev->strips_len);
+			img->flags |= FP_IMG_PARTIAL;
 			g_slist_free_full(aesdev->strips, g_free);
 			aesdev->strips = NULL;
 			aesdev->strips_len = 0;