dmaengine: zynqmp_dma: Fix race condition in the probe

Incase of interrupt property is not present,
Driver is trying to free an invalid irq,
This patch fixes it by adding a check before freeing the irq.

Signed-off-by: Kedareswara rao Appana <appanad@xilinx.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>