arm64: dts: ti: iot2050*: Clarify GPL-2.0 as GPL-2.0-only

arm64: dts: ti: iot2050*: Clarify GPL-2.0 as GPL-2.0-only

SPDX identifier GPL-2.0 has been deprecated since license list version
3.0. Use GPL-2.0-only to be specific.

Cc: Chao Zeng <chao.zeng@siemens.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Le Jin <le.jin@siemens.com>
Acked-by: Jan Kiszka <jan.kiszka@siemens.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20240122145539.194512-16-nm@ti.com
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>