website: update device_name parameter description

Signed-off-by: Mikhail Ushanov <gm.mephisto@gmail.com>

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

@@ -169,7 +169,8 @@ each category, the available configuration keys are alphabetized.
         every build.
 
     -   `device_name` (string) - The device name exposed to the instance (for
-        example, `/dev/sdh` or `xvdh`). Required when specifying `volume_size`.
+        example, `/dev/sdh` or `xvdh`). Required for every device in the
+        block device mapping.
 
     -   `encrypted` (boolean) - Indicates whether to encrypt the volume or not
 

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

@@ -83,7 +83,8 @@ builder.
         every build.
 
     -   `device_name` (string) - The device name exposed to the instance (for
-        example, `/dev/sdh` or `xvdh`). Required when specifying `volume_size`.
+        example, `/dev/sdh` or `xvdh`). Required for every device in the
+        block device mapping.
 
     -   `encrypted` (boolean) - Indicates whether to encrypt the volume or not
 

website/source/docs/builders/amazon-ebssurrogate.html.md

@@ -76,7 +76,8 @@ builder.
         every build.
 
     -   `device_name` (string) - The device name exposed to the instance (for
-        example, `/dev/sdh` or `xvdh`). Required when specifying `volume_size`.
+        example, `/dev/sdh` or `xvdh`). Required for every device in the
+        block device mapping.
 
     -   `encrypted` (boolean) - Indicates whether to encrypt the volume or not
 

website/source/docs/builders/amazon-ebsvolume.html.md

@@ -63,7 +63,8 @@ builder.
     device mappings to the AMI. The block device mappings allow for keys:
 
     -   `device_name` (string) - The device name exposed to the instance (for
-        example, `/dev/sdh` or `xvdh`). Required when specifying `volume_size`.
+        example, `/dev/sdh` or `xvdh`). Required for every device in the
+        block device mapping.
 
     -   `delete_on_termination` (boolean) - Indicates whether the EBS volume is
         deleted on instance termination.

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

@@ -105,7 +105,8 @@ builder.
         every build.
 
     -   `device_name` (string) - The device name exposed to the instance (for
-        example, `/dev/sdh` or `xvdh`). Required when specifying `volume_size`.
+        example, `/dev/sdh` or `xvdh`). Required for every device in the
+        block device mapping.
 
     -   `encrypted` (boolean) - Indicates whether to encrypt the volume or not