[media] staging: solo6x10: fix for sparse warning message

Define jpeg_dqt as static.

Signed-off-by: Anthony DeStefano <adx@fastmail.fm>
Signed-off-by: Ismael Luceno <ismael.luceno@corp.bluecherry.net>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>