mfd: ti-lmu: Use managed resource for everything

This replaces all remaining unmanaged resources with device
managed ones, so that the remove function is no longer needed.
This makes the code slightly shorter and fixes two problems:

 1. The hardware is disabled after the child devices have
    been removed. Previously there was a potential race
    condition.
 2. The hardware is disabled when mfd_add_devices fails
    during probe.

Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Lee Jones <lee.jones@linaro.org>