Fix below warning when CONFIG_OF=n:

drivers/regulator/stm32-pwr.c:169:34: warning: ‘stm32_pwr_of_match’ defined but not used [-Wunused-const-variable=]
  169 | static const struct of_device_id stm32_pwr_of_match[] = {
      |                                  ^~~~~~~~~~~~~~~~~~
Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
Link: https://lore.kernel.org/r/20200821111726.38e0e746@xhacker.debianSigned-off-by: Mark Brown <broonie@kernel.org>