ARM: OMAP: omap_device: don't attempt late suspend if no driver bound

Currently, the omap_device PM domain layer uses the late suspend and
early resume callbacks to ensure devices are in their low power
states.

However, this is attempted even in cases where a driver probe has
failed.  If a driver's ->probe() method fails, the driver is likely in
a state where it is not expecting its runtime PM callbacks to be
called, yet currently the omap_device PM domain code attempts to call
the drivers callbacks.

To fix, use the omap_device driver_status field to check whether a
driver is bound to the omap_device before attempting to trigger driver
callbacks.

Reviewed-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>