Allow userspace programs on ppc64 to use the (privileged) mfpvr instruction
to determine the processor type.  At the moment it emulates the instruction
to provide the real PVR value, though it could be made to lie in future if
for some reason we wish to restrict what CPU features userspace uses.

If nothing else this means that some existing ppc32 applications will now
run on a 64-bit kernel (the 32-bit kernel has long supported this
emulation).  It will also be necessary for ppc64 perfctr support, where
userspace requires finer-grained cpu type information than the kernel in
order to correctly program the performance monitor control registers.
Signed-off-by: David Gibson <dwg@au1.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>