[LinuxBIOS] about make LinuxBIOS 64bit for Opteron

[Lu, Yinghai]

I'm thinking to make LinuxBIOS to run at 64 bit mode so
it can access 40 bit address in one instruction

we just need to 
1. change entry32.inc to entry64.inc...
2. change secondary.S to support 64 bit
3. change most code32 to code64

The problem is that we may need make Etherboot and mkelfImage to support
64 bit too...

how do you think about it?

YH