page-pipe: drop unused PP_HOLE_ZERO flag

travis-ci: success for revert zero pagemaps
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

criu/include/page-pipe.h

@@ -102,7 +102,6 @@ struct page_pipe_buf {
 };
 
 #define PP_HOLE_PARENT (1 << 0)
-#define PP_HOLE_ZERO   (1 << 1)
 
 struct page_pipe {
 	unsigned int nr_pipes;	/* how many page_pipe_bufs in there */