media: s5p-jpeg: Constify struct v4l2_m2m_ops

The only usage of the v4l2_m2m_ops structs is to pass their address to
v4l2_m2m_init() which takes a pointer to const struct v4l2_m2m_ops as
argument. Make them const to allow the compiler to put them in read-only
memory.

Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>