fpga: zynqmp: Fix the nonsecure bitstream loading issue

Xilfpga library expects the size of bitstream in a pointer
but currenly we are passing the size as a value. This patch
fixes this issue.

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