thermal/drivers/tsens: Make tsens_xxxx_nvmem static

This patch fixes the following sparse warnings:

drivers/thermal/qcom/tsens-v1.c:24:40: sparse: warning: symbol 'tsens_qcs404_nvmem' was not declared. Should it be static?
drivers/thermal/qcom/tsens-v0_1.c:26:40: sparse: warning: symbol 'tsens_8916_nvmem' was not declared. Should it be static?
drivers/thermal/qcom/tsens-v0_1.c:42:40: sparse: warning: symbol 'tsens_8974_nvmem' was not declared. Should it be static?
drivers/thermal/qcom/tsens-v0_1.c:64:40: sparse: warning: symbol 'tsens_8974_backup_nvmem' was not declared. Should it be static?

No functional change intended.

Signed-off-by: Min-Hua Chen <minhuadotchen@gmail.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20230713160415.149381-1-minhuadotchen@gmail.com