x86: extended "flags" to show virtualization HW feature in /proc/cpuinfo

x86: extended "flags" to show virtualization HW feature in /proc/cpuinfo

The hardware virtualization technology evolves very fast. But currently
it's hard to tell if your CPU support a certain kind of HW technology
without digging into the source code.

The patch add a new catagory in "flags" under /proc/cpuinfo. Now "flags"
can indicate the (important) HW virtulization features the CPU supported
as well.

Current implementation just cover Intel VMX side.

Signed-off-by: Sheng Yang <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>