Compound controls are controls that can be used for compound and array
types. This allows for more compound data structures to be used with the
control framework.

The existing V4L2_CTRL_FLAG_NEXT_CTRL flag will only enumerate non-compound
controls, so a new V4L2_CTRL_FLAG_NEXT_COMPOUND flag is added to enumerate
compound controls. Set both flags to enumerate any control (compound or not).

Compound control types will start at V4L2_CTRL_COMPOUND_TYPES. In addition, any
control that uses the new 'ptr' field or the existing 'string' field will have
flag V4L2_CTRL_FLAG_HAS_PAYLOAD set.

While not strictly necessary, adding that flag makes life for applications
a lot simpler. If the flag is not set, then the control value is set
through the value or value64 fields of struct v4l2_ext_control, otherwise
a pointer points to the value.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Reviewed-by: NSylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>