Remove duplicate / unused #defines on AM335x boards

As part of a review of a recent patch to add a new AM335x board, Tom
found several duplicate and/or unused #defines.

This patch simply removes them.

The two affected configs have been recompiled to check nothing was
broken (from a compilation point of view !!)

Reported-by: Tom Rini <trini@ti.com>
Signed-off-by: Mark Jackson <mpfj-list@mimc.co.uk>