we no longer use hbird_eval to stand for board using by
nuclei fpga development boards, we are now using nuclei_fpga_eval
to stand for it.

nowadays the fpga bitstream cpu freq is 16MHz, and uart tx/rx
both works at 115200bps, so we change the baudrate to 115200bps
Signed-off-by: Huaqi Fang <578567190@qq.com>