V4L/DVB (12421): drivers/media/video/gspca: introduce missing kfree

Error handling code following a kmalloc should free the allocated data.

Signed-off-by: Julia Lawall <julia@diku.dk>
Acked-by: Erik Andrén <erik.andren@gmail.com>
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>