sky130 HDLL: added more cells to the TRISTATE_CELLS variable

sky130/librelane/sky130_fd_sc_hdll/config.tcl

diff --git a/sky130/librelane/sky130_fd_sc_hdll/config.tcl b/sky130/librelane/sky130_fd_sc_hdll/config.tcl
index ba66d97..8edd4e4 100755
--- a/sky130/librelane/sky130_fd_sc_hdll/config.tcl
+++ b/sky130/librelane/sky130_fd_sc_hdll/config.tcl
@@ -45,4 +45,4 @@
 
 set ::env(PDN_RAIL_WIDTH) 0.48
 
-set ::env(TRISTATE_CELLS) "$::env(STD_CELL_LIBRARY)__ebuf* $::env(STD_CELL_LIBRARY)__einv*"
+set ::env(TRISTATE_CELLS) "$::env(STD_CELL_LIBRARY)__ebuf* $::env(STD_CELL_LIBRARY)__einv* $::env(STD_CELL_LIBRARY)__muxb*"