media: uapi: Add V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS control

The number of 'entry point offset' could be very variable.
Rather than use a large static array define a v4l2 dynamic array
of U32 (V4L2_CTRL_TYPE_U32).
The number of entry point offsets is reported by the elems field
and in struct v4l2_ctrl_hevc_slice_params.num_entry_point_offsets
field.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>