pinctrl: mediatek: pinctrl-mtk-common-v2: Mark 'mtk_default_register_base_names' as __maybe_unused

Not all sourcefiles which end up including pinctrl-mtk-common-v2.h make use
of 'mtk_default_register_base_names' and there is nowhere we can place the
definition to void the need for __maybe_unused except its own headerfile,
which seems like overkill.  So instead we tell the compiler that it's okay
for it to be unused by some of the consumers.

Fixes the following W=1 kernel build warning(s):

 In file included from drivers/pinctrl/mediatek/pinctrl-mtk-common-v2.c:19:
 drivers/pinctrl/mediatek/pinctrl-mtk-common-v2.h:83:27: warning: ‘mtk_default_register_base_names’ defined but not used [-Wunused-const-variable=]
 83 | static const char const mtk_default_register_base_names[] = {
 | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 In file included from drivers/pinctrl/mediatek/pinctrl-moore.h:25,
 from drivers/pinctrl/mediatek/pinctrl-moore.c:12:
 drivers/pinctrl/mediatek/pinctrl-mtk-common-v2.h:83:27: warning: ‘mtk_default_register_base_names’ defined but not used [-Wunused-const-variable=]
 83 | static const char const mtk_default_register_base_names[] = {
 | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 In file included from drivers/pinctrl/mediatek/pinctrl-paris.h:27,
 from drivers/pinctrl/mediatek/pinctrl-paris.c:15:
 drivers/pinctrl/mediatek/pinctrl-mtk-common-v2.h:83:27: warning: ‘mtk_default_register_base_names’ defined but not used [-Wunused-const-variable=]
 83 | static const char const mtk_default_register_base_names[] = {
 | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 In file included from drivers/pinctrl/mediatek/pinctrl-paris.h:27,
 from drivers/pinctrl/mediatek/pinctrl-mtk-mt6797.h:15,
 from drivers/pinctrl/mediatek/pinctrl-mt6797.c:13:
 drivers/pinctrl/mediatek/pinctrl-mtk-common-v2.h:83:27: warning: ‘mtk_default_register_base_names’ defined but not used [-Wunused-const-variable=]
 83 | static const char const mtk_default_register_base_names[] = {
 | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 In file included from drivers/pinctrl/mediatek/pinctrl-paris.h:27,
 from drivers/pinctrl/mediatek/pinctrl-mtk-mt8183.h:12,
 from drivers/pinctrl/mediatek/pinctrl-mt8183.c:9:
 drivers/pinctrl/mediatek/pinctrl-mtk-common-v2.h:83:27: warning: ‘mtk_default_register_base_names’ defined but not used [-Wunused-const-variable=]
 83 | static const char const mtk_default_register_base_names[] = {
 | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 In file included from drivers/pinctrl/mediatek/pinctrl-paris.h:27,
 from drivers/pinctrl/mediatek/pinctrl-mtk-mt6765.h:12,
 from drivers/pinctrl/mediatek/pinctrl-mt6765.c:10:
 drivers/pinctrl/mediatek/pinctrl-mtk-common-v2.h:83:27: warning: ‘mtk_default_register_base_names’ defined but not used [-Wunused-const-variable=]
 83 | static const char const mtk_default_register_base_names[] = {
 | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Sean Wang <sean.wang@kernel.org>
Cc: Sean Wang <sean.wang@kernel.org>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: linux-mediatek@lists.infradead.org
Link: https://lore.kernel.org/r/20200713144930.1034632-11-lee.jones@linaro.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/mediatek/pinctrl-mtk-common-v2.h

@@ -80,7 +80,7 @@ enum {
 	DRV_GRP_MAX,
 };
 
-static const char * const mtk_default_register_base_names[] = {
+static const char * const mtk_default_register_base_names[] __maybe_unused = {
 	"base",
 };