vendor.lattice_{ecp5,machxo_2_3l}: fix hierarchy seperator in sdc files

Author: anuejn

nmigen/vendor/lattice_ecp5.py

@@ -237,6 +237,7 @@ class LatticeECP5Platform(TemplatedPlatform):
             {{get_override("add_preferences")|default("# (add_preferences placeholder)")}}
         """,
         "{{name}}.sdc": r"""
+            set_hierarchy_separator {/}
             {% for net_signal, port_signal, frequency in platform.iter_clock_constraints() -%}
                 {% if port_signal is not none -%}
                     create_clock -name {{port_signal.name|tcl_escape}} -period {{1000000000/frequency}} [get_ports {{port_signal.name|tcl_escape}}]

nmigen/vendor/lattice_machxo_2_3l.py

@@ -104,6 +104,7 @@ class LatticeMachXO2Or3LPlatform(TemplatedPlatform):
             {{get_override("add_preferences")|default("# (add_preferences placeholder)")}}
         """,
         "{{name}}.sdc": r"""
+            set_hierarchy_separator {/}
             {% for net_signal, port_signal, frequency in platform.iter_clock_constraints() -%}
                 {% if port_signal is not none -%}
                     create_clock -name {{port_signal.name|tcl_escape}} -period {{1000000000/frequency}} [get_ports {{port_signal.name|tcl_escape}}]