regulator: add missing 'static inline' to a helper's stub

The build fails when CONFIG_REGULATOR is not selected because the stub
for regulator_bulk_set_supply_names() is missing the 'static inline'
attribute.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Link: https://lore.kernel.org/r/20190902151332.28058-1-brgl@bgdev.pl


Signed-off-by: Mark Brown <broonie@kernel.org>