[POWERPC] Add mpc866ads board-specific bits to arch/powerpc

This add support of the Freescale mpc86xads reference board to
arch/powerpc. Supported SMC1 and SMC2 (UART and serial console), FEC
100Mbps Ethernet, SCC1 Ethernet (10Mbps hdx)

Signed-off-by: Vitaly Bordug <vbordug@ru.mvista.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>