loader: Update 1.0 checking mechanism

The loader will now get vkEnumerateInstanceVersion from the ICD by
calling the ICD's GetInstanceProcAddr function.
diff --git a/loader/loader.c b/loader/loader.c
index 3b58a89..d4e0e02 100644
--- a/loader/loader.c
+++ b/loader/loader.c
@@ -5170,7 +5170,7 @@
         // Get the driver version from vkEnumerateInstanceVersion
         uint32_t icd_version = VK_API_VERSION_1_0;
         PFN_vkEnumerateInstanceVersion icd_enumerate_instance_version = (PFN_vkEnumerateInstanceVersion)
-            loader_platform_get_proc_address(icd_term->scanned_icd->handle, "vkEnumerateInstanceVersion");
+            icd_term->scanned_icd->GetInstanceProcAddr(NULL, "vkEnumerateInstanceVersion");
         VkResult icd_result = VK_SUCCESS;
         if (icd_enumerate_instance_version != NULL) {
             icd_result = icd_enumerate_instance_version(&icd_version);