opencv: remove DEFAULT_PREFERENCE = "-1" for 3.1
opencv: remove DEFAULT_PREFERENCE = "-1" for 3.1

The opencv 2.4 has been blacklisted, 3.1 should be the default choice
for both opencv and lib32-opencv.

Signed-off-by: Wenzong Fan <f66bf62bd6ae2fe84a21d414af2ae81bdc552ed9@windriver.com>
Signed-off-by: Martin Jansa <516df3ff67e1fa5d153800b15fb204c0a1a389dc@gmail.com>

victronenergy/meta-openembedded,openembedded/meta-openembedded,mrchapp/meta-openembedded,openembedded/meta-openembedded,mrchapp/meta-openembedded,victronenergy/meta-openembedded,victronenergy/meta-openembedded,lgirdk/meta-openembedded,rehsack/meta-openembedded,lgirdk/meta-openembedded,amery/meta-openembedded,schnitzeltony/meta-openembedded,mrchapp/meta-openembedded,amery/meta-openembedded,amery/meta-openembedded,victronenergy/meta-openembedded,schnitzeltony/meta-openembedded,moto-timo/meta-openembedded,schnitzeltony/meta-openembedded,sigma-embedded/elito-org.openembedded.meta,kraj/meta-openembedded,openembedded/meta-openembedded,schnitzeltony/meta-openembedded,kraj/meta-openembedded,amery/meta-openembedded,lgirdk/meta-openembedded,victronenergy/meta-openembedded,VCTLabs/meta-openembedded,mrchapp/meta-openembedded,VCTLabs/meta-openembedded,kraj/meta-openembedded,kraj/meta-openembedded,moto-timo/meta-openembedded,moto-timo/meta-openembedded,lgirdk/meta-openembedded,amery/meta-openembedded,rehsack/meta-openembedded,rehsack/meta-openembedded,openembedded/meta-openembedded,rehsack/meta-openembedded,rehsack/meta-openembedded,amery/meta-openembedded,VCTLabs/meta-openembedded,sigma-embedded/elito-org.openembedded.meta,mrchapp/meta-openembedded,sigma-embedded/elito-org.openembedded.meta,rehsack/meta-openembedded,VCTLabs/meta-openembedded,schnitzeltony/meta-openembedded,rehsack/meta-openembedded,victronenergy/meta-openembedded,sigma-embedded/elito-org.openembedded.meta,sigma-embedded/elito-org.openembedded.meta,moto-timo/meta-openembedded,sigma-embedded/elito-org.openembedded.meta,mrchapp/meta-openembedded,lgirdk/meta-openembedded,VCTLabs/meta-openembedded,amery/meta-openembedded,schnitzeltony/meta-openembedded,schnitzeltony/meta-openembedded,kraj/meta-openembedded,sigma-embedded/elito-org.openembedded.meta,openembedded/meta-openembedded,VCTLabs/meta-openembedded,openembedded/meta-openembedded,openembedded/meta-openembedded,mrchapp/meta-openembedded,lgirdk/meta-openembedded,victronenergy/meta-openembedded,VCTLabs/meta-openembedded,moto-timo/meta-openembedded,VCTLabs/meta-openembedded,amery/meta-openembedded,lgirdk/meta-openembedded,openembedded/meta-openembedded,kraj/meta-openembedded,kraj/meta-openembedded