Support ARC firmware

[lenticularis39]

AlphaServer ES40 supports two types of BIOS - SRM and ARC, the former being used for most operating systems, while the latter is required to run Windows NT and can also boot Linux. Currently only SRM firmware works - attempting to switch over to ARC freezes the console, leaving the SRM prompt accessible from another terminal:

AlphaServer ES40 Console V7.3-1, built on Feb 27 2007 at 12:57:47
P00>>>alphabios
loading ARC firmware
starting console on CPU 0
initialized idle PCB
initializing idle process PID
lowering IPL
CPU 0 speed is 800 MHz
create powerup

[lenticularis39]

As discovered by neozeed in #95, the issue is that in the stock ROM, there is apparently no ARC. Continuing with the progress in the other issue.