xilinx_dff to account for R over CE priority

passes/pmgen/xilinx_dff.pmg

diff --git a/passes/pmgen/xilinx_dff.pmg b/passes/pmgen/xilinx_dff.pmg
index 0b97af8..f5637d4 100644
--- a/passes/pmgen/xilinx_dff.pmg
+++ b/passes/pmgen/xilinx_dff.pmg
@@ -3,6 +3,7 @@
 match fd
 	select fd->type.in(\FDRE)
 	select port(fd, \R).is_fully_zero()
+	select port(fd, \CE).is_fully_ones()
 endmatch
 
 match lut