[media] ak881x: simplify standard checks

Simplify confusing conditions. This also swaps the checks for NTSC and PAL:
to be consistent with other drivers check for NTSC first. So if the user
sets both NTSC and PAL bits, then NTSC wins.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>