iceblk-driver and icenet-driver may need to be updated

[xingyuli9961]

I'm currently working on the running some customized risc-v linux kernel on FireSim. I realized that there's a structural changes of the folders and some previous code should be updated accordingly.
Currently, in the Makefile's of the iceblk-driver and icenet-driver under firesim/sw/firesim-software/boards/firechip/drivers/, it says:
"LINUXSRC=../../../../riscv-linux"
However, it should be
"LINUXSRC= ../../linux "
in order to make the program compile inside its own folder.

Note: if I use the FireMarshal flow, it provides updated path and everything works well. This is just a trivial reminder to keep codes more consistent.