Update ezgl to use submodules

Author: AmirhosseinPoolad

.gitmodules

@@ -6,3 +6,7 @@
 [submodule "libs/EXTERNAL/sockpp"]
 	path = libs/EXTERNAL/sockpp
 	url = https://github.com/w0lek/sockpp.git
+
+[submodule "libs/EXTERNAL/libezgl"]
+	path = libs/EXTERNAL/libezgl
+	url = https://github.com/verilog-to-routing/ezgl.git

dev/subtree_config.xml

@@ -24,11 +24,6 @@
         internal_path="libs/EXTERNAL/libtatum"
         external_url="https://github.com/verilog-to-routing/tatum.git"
         default_external_ref="master"/>
-    <subtree
-        name="libezgl"
-        internal_path="libs/EXTERNAL/libezgl"
-        external_url="https://github.com/mariobadr/ezgl.git"
-        default_external_ref="master"/>
     <subtree
         name="capnproto"
         internal_path="libs/EXTERNAL/capnproto"