staging: hikey9xx: hi6421v600-regulator: get rid of an static data

Move it to be inside the private data struct.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/ff8b6852c788fd476743eb4ce556e4a97f4b928e.1611212783.git.mchehab+huawei@kernel.org


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