driver-core: remove lock for platform devices during probe

During driver probe procedure, lock on the parent of
platform devices could be removed to make probe in parallel.

Change-Id: I5457869e056a55b51dd91937d6202947b13977eb
Signed-off-by: vkakani <vkakani@codeaurora.org>
Signed-off-by: Wei Li <weili@codeaurora.org>