package: use SPDX short identifier for OFL license

package: use SPDX short identifier for OFL license

We want to use SPDX identifier for license string as much as possible.
SPDX short identifier for OFLv1.0/OFLv1.1 is OFL-1.0/OFL-1.1.

This change is done using following command.
find . -name "*.mk" | xargs sed -ri '/LICENSE( )?[\+:]?=/s/OFLv([1]\.[0-1])/OFL-\1/g'

Signed-off-by: Rahul Bedarkar <rahulbedarkar89@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>