plat: xilinx: zynqmp: Add GET_CALLBACK_DATA function

Add GET_CALLBACK_DATA function again as now Linux driver
supports both mailbox as well as ISR method.

Signed-off-by: Rajan Vaja <rajan.vaja@xilinx.com>
Signed-off-by: Jolly Shah <jolly.shah@xilinx.com>
Change-Id: Ieb99d61976e1cb718fcd1021d9cf4958e7556c81
3 files changed