~ruther/vhdl-spi-2

ref: c7e760505de065eff00a855e1ebf55c0bbe8e192 vhdl-spi-2/hdl_spi/src d---------
fix: master_ctrl_rst_n shou be used, not master_ctrl_rst, start_clock is split
fix: do not pass rx_serial_o from spi_multiplexor when not enabled
fix: prevent slave ctrl sending X's
feat: implement masterslave spi switch peripheral
feat: implement initial hdl_spi