Add - comment for max routing layer M5 (M6 needs to be expose for power grid connection)

Signed-off-by: louiic <[email protected]>

Author: louiic

flow/designs/asap7/mock-array-big/Element/config.mk

@@ -17,4 +17,6 @@ export IO_CONSTRAINTS = designs/asap7/mock-array-big/Element/io.tcl
 
 export PDN_TCL = designs/asap7/mock-array-big/Element/pdn.tcl
 
+# max routing layer need to be set to M5, since M6 is needed for next level up to connect
+# to the ring and stipe
 export MAX_ROUTING_LAYER = M5