opencv: Make 3.0 version default preference
opencv: Make 3.0 version default preference

Default preference is set back to default value of "0" to allow upgrading to
OpenCV 3.0 instead of being locked to version 2.4.

Signed-off-by: Antony Vance <e3c1cf8c7ebedb024ba7125904c0de592e6fdff9@ni.com>

ni/meta-nilrt,ni/meta-nilrt,ni/meta-nilrt,ni/meta-nilrt,ni/meta-nilrt