pinctrl: Minimize SPDX hamming distance

OK so some automatic scripts were fixing the SPDX tags in
the mainline branch while we were patching other stuff,
and yeah it is more correct to have "GPL-2.0-only" rather
than "GPL-2.0" so let's conform to what is already upstream
so we don't end up getting the wrong license on the merged
result later.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/nomadik/Kconfig

 # SPDX-License-Identifier: GPL-2.0-only
-
 if ARCH_U8500
 
 config PINCTRL_ABX500

drivers/pinctrl/pinctrl-coh901.c

-// SPDX-License-Identifier: GPL-2.0
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * U300 GPIO module.
  *

drivers/pinctrl/pinctrl-u300.c

-// SPDX-License-Identifier: GPL-2.0
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * Driver for the U300 pin controller
  *