regulator: core: Move helpers for drivers out into a separate file

Reduce the size of core.c a bit.

Signed-off-by: Mark Brown <broonie@linaro.org>
diff --git a/drivers/regulator/Makefile b/drivers/regulator/Makefile
index ba4a3cf..c6558ce 100644
--- a/drivers/regulator/Makefile
+++ b/drivers/regulator/Makefile
@@ -3,7 +3,7 @@
 #
 
 
-obj-$(CONFIG_REGULATOR) += core.o dummy.o fixed-helper.o
+obj-$(CONFIG_REGULATOR) += core.o dummy.o fixed-helper.o helpers.o
 obj-$(CONFIG_OF) += of_regulator.o
 obj-$(CONFIG_REGULATOR_FIXED_VOLTAGE) += fixed.o
 obj-$(CONFIG_REGULATOR_VIRTUAL_CONSUMER) += virtual.o