[PATCH] ARM: dts: imx7s-warp: use SPDX-License-Identifier

On Tue, Aug 28, 2018 at 2:06 PM, Pierre-Jean Texier
[off-list ref] wrote:

Adopt the SPDX license identifier headers to ease
license compliance management.

Signed-off-by: Pierre-Jean Texier <redacted>

Reviewed-by: Fabio Estevam <redacted>