arm: sunxi: Enable DRAM ODT by default on H3/H5

Most of the boards we support with H3/H5 enable DRAM on-die termination,
which is consistent with the high DRAM clocks that are used.

Make it the default (like it's done for other similar platforms) instead
of defining it in each defconfig.

Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Reviewed-by: Jagan Teki <jagan@openedev.com>