msm:ipa: Fix to slab out of bounds access

Accessing of incorrect structure pointer is causing
slab-out-of-bounds access, fixed issue by accessing
the correct structure pointer.

Change-Id: I23d3c9afbbabba88be92ef5cae83c4708a211e88
Acked-by: Ashok Vuyyuru <avuyyuru@qti.qualcomm.com>
Signed-off-by: Mohammed Javid <mjavid@codeaurora.org>