msm: ipa: remove extra mhi_device_get_sync()

Remove the extra get() from mhi device to allow LPM.

Change-Id: I5026361ad569985adf4e5a32893e35dbce862a54
Acked-by: Ady Abraham <adya@qti.qualcomm.com>
Signed-off-by: Skylar Chang <chiaweic@codeaurora.org>