mhi: core: create sysfs nodes before devices

Sysfs nodes should be created before devices as there is no
dependency and reverse order is maintained in device removals.

Change-Id: Ie8c9bb7323a89a1d76d5b016d6060ff9370e03a3
Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>