regulator: Guard of_regulator_bulk_get_all() with CONFIG_OF

regulator: Guard of_regulator_bulk_get_all() with CONFIG_OF

Since the definition is in drivers/regulator/of_regulator.c and compiled
only if CONFIG_OF is enabled, building the consumer driver without
CONFIG_OF and with CONFIG_REGULATOR will result in below build error:

ERROR: modpost: "of_regulator_bulk_get_all" [drivers/pci/pwrctrl/pci-pwrctl-slot.ko] undefined!

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202412181640.12Iufkvd-lkp@intel.com/
Fixes: 27b9ecc7a9ba ("regulator: Add of_regulator_bulk_get_all")
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Link: https://patch.msgid.link/20250104115058.19216-2-manivannan.sadhasivam@linaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>