Restore "device type" for iOS internal.client.webrtc

This partially reverts a94ad2920c7aa645e6d81bc17f7a1be17fef4be7
because of failures in iOS Perf trybots.

Bug: webrtc:7156
Change-Id: Icaf10ffc2941419bd89481f1d5c8e377801b24eb
Reviewed-on: https://webrtc-review.googlesource.com/c/105626
Reviewed-by: Artem Titarenko <artit@webrtc.org>
Reviewed-by: Oleh Prypin <oprypin@webrtc.org>
Commit-Queue: Artem Titarenko <artit@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25142}

tools_webrtc/ios/internal.client.webrtc/iOS64_Debug.json

@@ -21,6 +21,7 @@
   "tests": [
     {
       "include": "real_device_tests.json",
+      "device type": "iPhone 6s",
       "os": "11.4.1",
       "dimensions": [
         {

tools_webrtc/ios/internal.client.webrtc/iOS64_Perf.json

@@ -21,6 +21,7 @@
   "tests": [
     {
       "include": "perf_tests.json",
+      "device type": "iPhone 7",
       "os": "11.4.1",
       "dimensions": [
         {

tools_webrtc/ios/internal.client.webrtc/iOS64_Release.json

@@ -22,6 +22,7 @@
   "tests": [
     {
       "include": "real_device_tests.json",
+      "device type": "iPhone 6s",
       "os": "11.4.1",
       "dimensions": [
         {