regulator: core kbuild files

This patch adds kernel build support for the regulator core.

Signed-off-by: Philipp Zabel <philipp.zabel@gmail.com>
Signed-off-by: Liam Girdwood <lg@opensource.wolfsonmicro.com>
diff --git a/drivers/Makefile b/drivers/Makefile
index 54ec5e7..a280ab3 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -97,3 +97,4 @@
 obj-$(CONFIG_OF)		+= of/
 obj-$(CONFIG_SSB)		+= ssb/
 obj-$(CONFIG_VIRTIO)		+= virtio/
+obj-$(CONFIG_REGULATOR)		+= regulator/