Apologies for the spam, resending as this appeared to break
the first time.

These are some initial patches to bugs I found attempting to
get a XIP kernel working on hardware:
 - 32-bit VexRiscv processor
 - kernel in SPI flash, at 0x00200000
 - 16MB of RAM at 0x10000000
 - MMU enabled
 
The system isn't actually booting yet; but at least the
initial memory management setup completes with these
patches as opposed to crashing almost straight away.