[POWERPC] 4xx: Add AMCC 460EX/460GT support to cputable.c & cpu_setup_44x.S

This patch adds basic support for the AMCC 460EX/460GT PPC's to arch/powerpc.
Currently those PPC's are still based on a 440 core and *not* a 460 core.

Here some basic features of those SoC's:

460EX:
- Up to 1.2GHz, 32kB L1 I-cache and D-cache, 256kB L2-cache, FPU
- 1 * PCI (max 66MHz), 2 * PCIe (one 4-lane, one 1-lane)
- 2 * GBit Ethernet with TCP/IP acceleration
- USB 2.0 Host/Device OTG and Host interface
- SATA controller
- Optional security feature

460GT (only changes to 460EX):
- 4 * GBit Ethernet with TCP/IP acceleration
- RapidIO
- No SATA
- No USB

Signed-off-by: Stefan Roese <sr@denx.de>
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>