media: videodev2.h: Add more field helper macros

Adds two helper macros:

V4L2_FIELD_IS_SEQUENTIAL: returns true if the given field type is
'sequential', that is a full frame is transmitted, or exists in
memory, as all top field lines followed by all bottom field lines,
or vice-versa.

V4L2_FIELD_IS_INTERLACED: returns true if the given field type is
'interlaced', that is a full frame is transmitted, or exists in
memory, as top field lines interlaced with bottom field lines.

Signed-off-by: Steve Longerbeam <slongerbeam@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>