staging: mfd: hi6421-spmi-pmic: get rid of unused OF properties

staging: mfd: hi6421-spmi-pmic: get rid of unused OF properties

There are several OF properties that aren't used by Hikey 970,
and some are not even used inside the driver.

So, drop them, as as this makes easier to document what's
actually used.

If latter needed, those could be re-added later.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/332f96c178b81bf1e9908a1da2127f043909ae0c.1597647359.git.mchehab+huawei@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>