fix(zynqmp): use common interface for eemi apis

Currently all EEMI API has its own implementation in TF-A which is
redundant. Most EEMI API implementation in TF-A does same work. It
prepares payload received from kernel, sends payload to firmware,
receives response from firmware and send response back to kernel.

So use common interface for EEMI APIs which has similar functionality.
This will optimize TF-A code.

Signed-off-by: Ronak Jain <ronak.jain@xilinx.com>
Change-Id: I07325644a1fae80211f2588d5807c21973f6d48f