Define default DDR location to which ATF has to compiled
if DEBUG option is enabled. This is required now, as the ATF cant fit
in OCM with DEBUG option enabled. The default value is 0x1000 and can be
used till 0x7ffff. User can still override as per wish/requirement
using current commandline options.

Signed-off-by: Jolly Shah <jollys@xilinx.com>