spi: spi-mtk-nor: make some internal variables static

Variables mtk_nor_caps_mt8173, mtk_nor_caps_mt8186 and
mtk_nor_caps_mt8192 are not declared.
Make them static.

Fixes: 5b177234 ("spi: spi-mtk-nor: improve device table for adding more capabilities")
Signed-off-by: Guochun Mao <guochun.mao@mediatek.com>
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/r/20220126091159.27513-1-guochun.mao@mediatek.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-mtk-nor.c

@@ -770,17 +770,17 @@ static const struct spi_controller_mem_ops mtk_nor_mem_ops = {
 	.exec_op = mtk_nor_exec_op
 };
 
-const struct mtk_nor_caps mtk_nor_caps_mt8173 = {
+static const struct mtk_nor_caps mtk_nor_caps_mt8173 = {
 	.dma_bits = 32,
 	.extra_dummy_bit = 0,
 };
 
-const struct mtk_nor_caps mtk_nor_caps_mt8186 = {
+static const struct mtk_nor_caps mtk_nor_caps_mt8186 = {
 	.dma_bits = 32,
 	.extra_dummy_bit = 1,
 };
 
-const struct mtk_nor_caps mtk_nor_caps_mt8192 = {
+static const struct mtk_nor_caps mtk_nor_caps_mt8192 = {
 	.dma_bits = 36,
 	.extra_dummy_bit = 0,
 };