powerpc/mpc85xx: Added B4460 support

B4460 differs from B4860 only in number of CPU cores,
hence used existing support for B4860.
B4460 has 2 PPC cores whereas B4860 has 4 PPC cores.

Signed-off-by: Shaveta Leekha <shaveta@freescale.com>
Signed-off-by: Sandeep Singh <Sandeep@freescale.com>
Signed-off-by: Poonam Aggrwal <poonam.aggrwal@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>