xilinx: Fix fpga region DT nodes name

fpga-full is not aligned with the latest dt-schema. Generic name
fpga-region should be used.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/78e6e3f287f79917eb92c6c74accbaf955526aad.1706791116.git.michal.simek@amd.com