[media] vivi: Don't depend on FONTS

CONFIG_FONTS has nothing to do with whether find_font() is defined.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Acked-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>