msm: ipa4: Don't decrease channel ref conunt for GCI channel

Because of decreasing channel reference count two times one
channel ref count value going to negetive value and failed to
deallocate this event ring. Add changes to avoid decreasing the
reference count for GCI channel.

Change-Id: Id85d476cb9ccf138dc3e5979395ce853d53dd317
Signed-off-by: Ashok Vuyyuru <avuyyuru@codeaurora.org>