[media] v4l2-ctrls: add support for compound types

This patch implements initial support for compound types.

The changes are fairly obvious: basic support for is_ptr types, the
type_is_int function is replaced by a is_int bitfield, and
v4l2_query_ext_ctrl is added.

Note that this patch does not yet add support for N-dimensional
arrays, that comes later. So v4l2_query_ext_ctrl just sets elems to
1 and nr_of_dims and dims[] are all zero.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>