Make SW prefetch flag a parameter again, and add code to make

Make SW prefetch flag a parameter again, and add code to make
it actually do something on FullCPU.  Still disabled, as it
causes detailed-boot to hang when you turn it on.

arch/alpha/isa_desc:
    Add EAComp and MemAcc pseudo-instructions to prefetch StaticInst.
cpu/simple_cpu/simple_cpu.hh:
    Changed prefetch() return type from Fault to void.

--HG--
extra : convert_revision : c7cb42682bfea6af117c87d4dfdb06176b6fe6b7