Linux does not boot with L1 and L2 disabled

[jzbydniewski]

Observed with HS58. When I disable L1 and L2 cache by setting ARC_CACHE=n I can see Linux doesn't boot. No signs of life are shown on UART console.

Debugging with gdb shows it crash with 'invalid mem access' message

backtrace:

I can't reproduce this on nSIM, but that's likely because it doesn't emulate L1/L2 anyway.