ram: rk3288: Initialize dram for TPL builds

Few of the rk3288 boards like tinker, vyasa are using
TPL, SPL bootchain so the dram initialization must needed
during TPL stage. So add proper ifconstruct to satisfy
both TPL, SPL and SPL-only bootchain boards.

This eventually fixing TPL to SPL handoff, otherwise missing
dram initilaztion at TPL stage would leads to SPL hang.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Reviewed-by: Kever <Yang&lt;kever.yang@rock-chips.com>