msm: mhi_dev: Update MBIM channel attribute

Remove restriction to expose the MBIM channel after a channel
connect. The group and owner permission is updated to
radio and radio during boot up and may cause the update
to not be reflected.

Change-Id: Id612fd24b41a414e59f149e9dd16eb17f0407ca5
Signed-off-by: Siddartha Mohanadoss <smohanad@codeaurora.org>