ARM: DRA7: Add hook in SoC initcalls to enable pm initialization

With consolidated code, now we can add the required hooks for
DRA7 to enable power management.

Signed-off-by: Rajendra Nayak <rnayak@ti.com>
[nm@ti.com: minor modifications]
Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Kevin Hilman <khilman@linaro.org>
Tested-by: Kevin Hilman <khilman@linaro.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>