[POWERPC] 4xx: Use virtual PVR value to init FPU on arch/ppc 440EP

This fixes arch/ppc 440EP platforms to setup the FPU correctly.  A virtual
PVR is used, as 440GR platforms share an identical hardware PVR value and do
not have an FPU.

Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>