ARM: BCM23550 SMP support

BCM23550 has a Cluster Dormant Control IP block that holds cores
in an idle state. Support a new CPU enable method in which the CDC is
accessed to bring the core online.

Signed-off-by: Raymond Ngun <raymond.ngun@broadcom.com>
Signed-off-by: Chris Brand <chris.brand@broadcom.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>