ARM: dts: am335x-boneblue: Enable eQEP

This enables the Enhanced Quadrature Encoder Pulse (eQEP) module for
connectors E1, E2 and E3 on BeagleBone Blue.

Signed-off-by: David Lechner <david@lechnology.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>