msm: ipa: fix bug in routing table deletion

When a routing table is ready to be deleted, lookup was
failing due to an erroneous check on return value. This
commit fixes that bug.

Change-Id: I1bd12553d60163ca77d7770e2370790e4f9a3b05
Signed-off-by: Ravi Gummadidala <rgummadi@codeaurora.org>