Sitlinv STLV7325 is a board with XC7K325T-FFG676.
Add support for it.
The board does not have JTAG cables on board, however its vendor
provides an option to buy a FT4232-based JTAG cable with the board, so
the default cable is set to ft4232.
Signed-off-by: Icenowy Zheng <uwu@icenowy.me>