[POWERPC] 4xx: Move 440EP(x) FPU setup from head_44x to cpu_setup_4xx

The PowerPC 440EP(x) FPU init is currently done in head_44x
under ifdefs. Since we should support more then one board
in the same kernel, we move FPU initialization code from head_44x
to cpu_setup_44x and add cpu_setup callbacks for 440EP(x).

Signed-off-by: Valentine Barshak <vbarshak@ru.mvista.com>
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>