staging: regulator: hi6421v600-regulator: add it to the building system

Change the binding logic to ensure that the PMIC SPMI
driver will run before the regulator code and add it to the
building system.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/2992dc49945dcfb07c4bd96fa5c288c4e679701a.1597647359.git.mchehab+huawei@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>