media: hevc: Fix dependent slice segment flags

Dependent slice segment flag for PPS control is misnamed. It should have
"enabled" at the end. It only tells if this flag is present in slice
header or not and not the actual value.

Fix this by renaming the PPS flag and introduce another flag for slice
control which tells actual value.

Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>