Remove driver files that generate compiler warnings from the RISC-V_Renode_Emulator_S...

Remove driver files that generate compiler warnings from the RISC-V_Renode_Emulator_SoftConsole project.
Update RISC-V ports so the interrupt stack is set to a known value before the scheduler is started if the interrupt stack is statically defined rather than re-using the main.c() stack.

git-svn-id: https://svn.code.sf.net/p/freertos/code/trunk@2754 1d2547de-c912-0410-9cb9-b8ca96c0e9e2