[PPC64] Allow emulation of mfpvr on ppc64 kernel

[Paul Mackerras]

Ingo Oeser writes:

> Why not putting the required information into the AUX table
> when executing your ELF programs? I loved this feature in the
> ix86 arch.

We do put an AT_HWCAP entry in the aux table, which is a bitmap of
features supported by the cpu.  But for some applications, such as
programming the performance monitor hardware, you need to know the
specific CPU model and version, and this is a way to provide that
information.

Paul.