nangate45: use original LEF to restore antenna info

Switch to NangateOpenCellLibrary.macro.lef which has antenna data
and remove the obsolete .mod.lef and .rect.lef files. Fixes #597

Author: alokkumardalei-wq

flow/platforms/nangate45/config.mk

@@ -5,7 +5,7 @@ export PROCESS = 45
 # Tech/Libs
 # ----------------------------------------------------
 export TECH_LEF = $(PLATFORM_DIR)/lef/NangateOpenCellLibrary.tech.lef
-export SC_LEF = $(PLATFORM_DIR)/lef/NangateOpenCellLibrary.macro.mod.lef
+export SC_LEF = $(PLATFORM_DIR)/lef/NangateOpenCellLibrary.macro.lef
 
 export LIB_FILES = $(PLATFORM_DIR)/lib/NangateOpenCellLibrary_typical.lib \
                      $(ADDITIONAL_LIBS)