Replace the 'rotation' property description by providing a definition
relative to the camera sensor pixel array coordinate system and the
captured scene.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>