video/fbdev: fix defio's fsync

commit 30ea9c5218651bc11cbdba7820be78f04e2d83bc upstream.

fb_deferred_io_fsync() returns the value of schedule_delayed_work() as
an error code, but schedule_delayed_work() does not return an error. It
returns true/false depending on whether the work was already queued.

Fix this by ignoring the return value of schedule_delayed_work().

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>