nfc: mrvl: use SPDX-License-Identifier

Use SPDX-License-Identifier: GPL-2.0-only, instead of hand writing it.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20210531073522.6720-3-krzysztof.kozlowski@canonical.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>