dmaengine: edma: Do not allocate memory for edma_rsv_info in case of DT boot

The channel/slot reservation is not supported when booted with DT so there
is not need to allocate memory.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>