fbdev: bf537-lq035: add missing blacklight properties type

Seems this new field was missed, probably due to this driver being merged
around the time this new backlight field was being added.  At any rate,
initial the type field to avoid ugly WARN() dumps.

Signed-off-by: Steven Miao <realmz6@gmail.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>