ddr: marvell: a38x: fix comment in conditional macro

The code was processed with unifdef utility to omit portions not
relevant to A38x and DDR3. This removes usage of many macros, including
A70X0, A80X0 and A3900. It seems that the unifdef utility did not remove
the macros from #else comment.

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Tested-by: Chris Packham <chris.packham@alliedtelesis.co.nz>