ARM: BCM: Add SMP support for Broadcom 4708

Add SMP support for Broadcom's 4708 SoCs.

Signed-off-by: Jon Mason <jonmason@broadcom.com>
Acked-by: Hauke Mehrtens <hauke@hauke-m.de>
Tested-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: Kapil Hali <kapilh@broadcom.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>