staging: mfd: hi6421-spmi-pmic: change the binding logic

Change the binding logic to ensure that the MFD driver
will be load after having the SPMI controller registered.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/eb50392ce68bb30f64c603572cdb9c91f93ea47b.1597647359.git.mchehab+huawei@kernel.org


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