spmi: hisi-spmi-controller: move driver from staging

The Hisilicon 6421v600 SPMI driver is ready for mainstream.

So, move it from staging.

Acked-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/35b9f9169889c1f4d51eff8bf2035450c9e02576.1624606660.git.mchehab+huawei@kernel.org


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