fpga: xilinx: Avoid using local intermediate buffer

Dont use local temporary buffer for printing out the
info instead use directly from memroy. This fixes the
issue of stack corruprion due to local buffer overflow.

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