Add eQEP0

This is taken from https://github.com/Teknoman117/beaglebot/blob/69a6a02ee277365734af40c063d6be2c14d46d4b/encoders/dts/bone_eqep0.dts. Similar operation is required for eqep1 and eqep2. Discussion found at https://groups.google.com/forum/#!searchin/beagleboard/eqep/beagleboard/Orp3tFcNgCc/mYacP_GkCQQJ.