powerpc/86xx: Correct Gianfar support for GE boards

The GE DTBs were not updated when the Gianfar driver was converted to an
of_platform_driver in commit b31a1d8b41513b96e9c7ec2f68c5734cef0b26a4. Update
the DTBs, adding the required TBI entries.

Signed-off-by: Martyn Welch <martyn.welch@ge.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>