firmware: scmi: voltage regulator

Implement voltage regulators interfaced by the SCMI voltage domain
protocol. The DT bindings are defined in the Linux kernel since
SCMI voltage domain and regulators patches [1] and [2] integration
in v5.11-rc7.

Link: [1] https://github.com/torvalds/linux/commit/0f80fcec08e9c50b8d2992cf26495673765ebaba
Link: [2] https://github.com/torvalds/linux/commit/2add5cacff3531e54c50b0832128299faa9f0563
Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>
diff --git a/drivers/power/regulator/Makefile b/drivers/power/regulator/Makefile
index 9d58112..b2f5972 100644
--- a/drivers/power/regulator/Makefile
+++ b/drivers/power/regulator/Makefile
@@ -30,3 +30,4 @@
 obj-$(CONFIG_DM_REGULATOR_TPS62360) += tps62360_regulator.o
 obj-$(CONFIG_$(SPL_)DM_REGULATOR_STPMIC1) += stpmic1.o
 obj-$(CONFIG_DM_REGULATOR_TPS65941) += tps65941_regulator.o
+obj-$(CONFIG_DM_REGULATOR_SCMI) += scmi_regulator.o