fpga: zynqmppl: Reuse invoke_smc routine

Reuse invoke_smc() routine which is already defined
instead of duplicating same at multiple places.

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