media: coda: jpeg: explicitly disable thumbnails in SEQ_INIT

Explicitly clear DEC_SEQ_JPG_THUMB_EN during sequence initialization.
Not clearing the register does not cause problems, since the only other
codec (MPEG-4 decode) that writes to this register happens to always
write 0 as well.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>