msm: ipa2: fix wrong check for memory allocation

Fix issue where after memory allocation, the wrong variable is tested for
memory allocation failure, which may result in NULL de-referencing.

Change-Id: Ibf221dfcd01fbdb5c953684c273f50f9059c30ac
CRs-Fixed: 1027443
Signed-off-by: Gidon Studinski <gidons@codeaurora.org>