Add GET_CALLBACK_DATA function to get IPI callback
data in Linux during init suspend callback.

Signed-off-by: Rajan Vaja <rajan.vaja@xilinx.com>
Signed-off-by: Jolly Shah <jolly.shah@xilinx.com>
Change-Id: Ieb60e561b5f656611f0702c43ba6a4296a012651