Fix namespace of PdkInfoProto to better reflect the intent.

Namespaces for protocol buffers should not be based on path-elements
but primarily on what they represent.
This proto has nothing to do with bazel nor rules, just hdl.

Author: hzeller

pdk/proto/pdk_info.proto

@@ -1,6 +1,6 @@
 syntax = "proto2";
 
-package bazel_rules_hdl.pdk;
+package hdl.pdk;
 
 message PdkInfoProto {
   repeated string cell_lef_paths = 1;