CHROMIUM: [media] v4l: Add private compound control type.

CHROMIUM: [media] v4l: Add private compound control type.

V4L2_CTRL_TYPE_PRIVATE is to be used for private driver compound
controls that use the "ptr" member of struct v4l2_ext_control.

BUG=chrome-os-partner:33728
TEST=build

Signed-off-by: Pawel Osciak <posciak@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/228988
Trybot-Ready: Tomasz Figa <tfiga@chromium.org>
Tested-by: Tomasz Figa <tfiga@chromium.org>
Reviewed-by: Wu-cheng Li <wuchengli@chromium.org>
Commit-Queue: Tomasz Figa <tfiga@chromium.org>

Change-Id: I44083b0216ef32629d12f0910e972a3e827a599a
Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
Signed-off-by: Yakir Yang <ykk@rock-chips.com>