Simplest method to transmit a file to FPGA

You can use system console for this with a JTAG to avalon master: https://www.altera.com/en_us/pdfs/literature/hb/qts/qts_qii53028.pdf

There are APIs called "master_read_to_file" and "master_write_from_file" that you can use to push a file down to memory in the FPGA and vice versa for the opposite direction. I also used to use Nios II for this sort of thing with something called host FS where I could have Nios open a file up on the host for read/write purposes over the JTAG channel but I have no clue if that's still supported. I suspect system console can move the data faster than host FS since I seem to recall host FS was only around 4kB/s back with the first generation USB blaster.