fpga: zynq: Add support for loading bitstream

Devcfg device requires to load bitstream in binary format.
But u-boot also has an option for loading bitstream in bit
format. Let's handle both cases by zynqpl driver.
Also add suport for loading partial bitstreams.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
fpga: zynqpl: Fix driver message

Use the same format for all prints in the driver.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>