Move the register helpers used to access the registers via p2wi resp.
rsb bus on the otherwise identical axp221 and axp223 pmics to a separate
file, so that they can be used by the upcoming standalone axp gpio driver
too.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Acked-by: Ian Campbell <ijc@hellion.org.uk>
