msm: gsi: Set cookie correctly for GCI channel TREs

Use the right index based on the cookie for GCI channel
TREs that are using the extra allocated buffers.

Change-Id: I19643223e4e496bf1b976b0bf73bbe3d8a1fe03a
Signed-off-by: Michael Adisumarta <madisuma@codeaurora.org>
1 file changed