arm: socfpga: Enhance FPGA program write rbf data with size >= 4 bytes

arm: socfpga: Enhance FPGA program write rbf data with size >= 4 bytes

Existing FPGA program write is always assume RBF data >= 32 bytes, so
any rbf data less than 32 bytes writing to FPGA would be failed.
This patch enhances the FPGA program write to support rbf data with
size >= 4 bytes.

Signed-off-by: Tien Fong Chee <tien.fong.chee@intel.com>