This reverts commit adf6e079.

Remove system PM methods which can race with runtime PM methods.

Also, as of v3.1, the PM domain level code for OMAP handles device
power state transistions automatically for devices, so drivers no
longer need to specifically call the bus/pm_domain methods themselves.
Signed-off-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>