This commit implements frame decimation for stk1160, which allows
to support format changes instead of a static frame size.

The stk1160 supports independent row and column decimation, in two
different modes:
 * set a number of rows/columns units to skip for each unit sent.
 * set a number of rows/columns units to send for each unit skipped.

This effectively allows to achieve different frame scaling ratios.

The unit number can be set to either two row/columns sent/skipped,
or four row/columns sent/skipped. Since the video format (UYVY)
has 4-bytes, using a unit number of two row/columns results
in frame color 'shifting', so set to four row/columns sent/skipped.
Signed-off-by: NMichael Stegemann <michael@stegemann.it>
Signed-off-by: NDale Hamel <dale.hamel@srvthe.net>
Signed-off-by: NEzequiel Garcia <ezequiel@vanguardiasur.com.ar>
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@osg.samsung.com>