media: hevc: Add sps_max_sub_layers_minus1 to v4l2_ctrl_hevc_sps

sps_max_sub_layers_minus1 is needed if the driver wishes to determine
whether or not a frame might be used for reference.

Signed-off-by: John Cox <jc@kynesim.co.uk>
Reviewed-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>