of: add devm_ functions for populate and depopulate

Lots of calls to of_platform_populate() are not unbalanced by a call
to of_platform_depopulate(). This create issues while drivers are
bind/unbind.

In way to solve those issues is to add devm_of_platform_populate()
which will call of_platform_depopulate() when the device is unbound
from the bus.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1487952874-23635-2-git-send-email-benjamin.gaignard@linaro.org