V4L/DVB (6976): drivers/media/radio/radio-sf16fmr2.c: fix error handling

video_register_device() returns -EFOO on errr, not -1.

Addresses http://bugzilla.kernel.org/show_bug.cgi?id=9699



Reported-By:  <devzero@web.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>