arm64: versal: fpga: Add PL bit stream load support

This patch adds PL bitstream load support for Versal platform. The PL
bitstream is loaded by making an SMC to ATF which in turn communicates
with platform firmware which configures and loads PL bitstream on to PL.

Signed-off-by: Siva Durga Prasad Paladugu <siva.durga.paladugu@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>