V4L/DVB (12441): siano: read buffer overflow

With mode DEVICE_MODE_RAW_TUNER a read occurs past the end of smscore_fw_lkup[].
Subsequently an attempt is made to load the firmware from the resulting
filename.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>