staging: mfd: hi6421-spmi-pmic: add it to the building system

Now that the driver is ready, place it at the build system.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/952e11ea1a33beaf67d6dc355d5c0f99ab4fb964.1597647359.git.mchehab+huawei@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/hikey9xx/Kconfig

 # SPDX-License-Identifier: GPL-2.0
 
+# to be placed at drivers/spmi
 config SPMI_HISI3670
 	tristate "Hisilicon 3670 SPMI Controller"
 	select IRQ_DOMAIN_HIERARCHY
@@ -8,3 +9,19 @@ config SPMI_HISI3670
 	  If you say yes to this option, support will be included for the
 	  built-in SPMI PMIC Arbiter interface on Hisilicon 3670
 	  processors.
+
+# to be placed at drivers/mfd
+config MFD_HI6421_SPMI
+	tristate "HiSilicon Hi6421v600 SPMI PMU/Codec IC"
+	depends on OF
+	select MFD_CORE
+	select REGMAP_MMIO
+	help
+	  Add support for HiSilicon Hi6421v600 SPMI PMIC. Hi6421 includes
+	  multi-functions, such as regulators, RTC, codec, Coulomb counter,
+	  etc.
+
+	  This driver includes core APIs _only_. You have to select
+	  individual components like voltage regulators under corresponding
+	  menus in order to enable them.
+	  We communicate with the Hi6421v600 via a SPMI bus.

drivers/staging/hikey9xx/Makefile

 # SPDX-License-Identifier: GPL-2.0
 
-obj-$(CONFIG_SPMI_HISI3670) += hisi-spmi-controller.o
+obj-$(CONFIG_SPMI_HISI3670)	+= hisi-spmi-controller.o
+obj-$(CONFIG_MFD_HI6421_SPMI)	+= hi6421-spmi-pmic.o