staging: regulator: hi6421v600-regulator: change the binding logic

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/aa40d443dfc6c8e69e4c36fa79d15459762924e4.1597647359.git.mchehab+huawei@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>