backlight: adp5520: rename common defines and typos

The common adp5520 mfd defines were namespaced to avoid collisions, so
update the define used in this driver accordingly.  The structs were also
renamed to fix a spelling typo.

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>