mx28evk: Remove unneeded 'undef'

There is no need to undef an option that is not enabled by default.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Marek Vasut <marex@denx.de>
Acked-by: Stefano Babic <sbabic@denx.de>
1 file changed