misc: Change vkGetProcAddr to vkGetDeviceProcAddr

Also cleanup layer/loader GPA's to only return device level entrypoints.
diff --git a/vulkan.py b/vulkan.py
index f18ab68..796a280 100755
--- a/vulkan.py
+++ b/vulkan.py
@@ -239,8 +239,8 @@
             [Param("VkInstance", "instance"),
              Param("const char*", "pName")]),
 
-        Proto("void*", "GetProcAddr",
-            [Param("VkPhysicalDevice", "gpu"),
+        Proto("void*", "GetDeviceProcAddr",
+            [Param("VkDevice", "device"),
              Param("const char*", "pName")]),
 
         Proto("VkResult", "CreateDevice",