Updated doc with config

website/source/docs/builders/amazon-chroot.html.markdown

@@ -122,7 +122,7 @@ each category, the available configuration keys are alphabetized.
   which forces Packer to find an open device automatically.
 
 * `enhanced_networking` (boolean) - Enable enhanced networking (SriovNetSupport) on
-  HVM-compatible AMIs.
+  HVM-compatible AMIs. If true, add `ec2:ModifyInstanceAttribute` to your AWS IAM policy.
 
 * `mount_path` (string) - The path where the volume will be mounted. This is
   where the chroot environment will be. This defaults to

website/source/docs/builders/amazon-ebs.html.markdown

@@ -94,7 +94,7 @@ each category, the available configuration keys are alphabetized.
   Leave this empty to allow Amazon to auto-assign.
 
 * `enhanced_networking` (boolean) - Enable enhanced networking (SriovNetSupport) on
-  HVM-compatible AMIs.
+  HVM-compatible AMIs. If true, add `ec2:ModifyInstanceAttribute` to your AWS IAM policy.
 
 * `iam_instance_profile` (string) - The name of an
   [IAM instance profile](http://docs.aws.amazon.com/IAM/latest/UserGuide/instance-profiles.html)

website/source/docs/builders/amazon-instance.html.markdown

@@ -134,7 +134,7 @@ each category, the available configuration keys are alphabetized.
   See the "custom bundle commands" section below for more information.
 
 * `enhanced_networking` (boolean) - Enable enhanced networking (SriovNetSupport) on
-  HVM-compatible AMIs.
+  HVM-compatible AMIs. If true, add `ec2:ModifyInstanceAttribute` to your AWS IAM policy.
 
 * `iam_instance_profile` (string) - The name of an
   [IAM instance profile](http://docs.aws.amazon.com/IAM/latest/UserGuide/instance-profiles.html)