Use tcl script instead of static xmls for the interface.
Easier to maintain and are not gitignored.
Rename spi_master to spi_engine because every interface should be
prefixed by the IP name; in this case, spi_engine.
Also, remove interface/*.sv files on make clean and git ignore them.
Signed-off-by: Jorge Marques <jorge.marques@analog.com>
Because the inferface signals which pass through the eval board's
Arduino connector are connected to level shifters the design
will not work at the maximum clk frequency of 48MHz. The maximum
tested frequency is 24MHz.