msm: ipa: Fix ipa3_wwan_xmit return type

This change will fix the error thrown by CFI for the return type of
ipa3_wwan_xmit.

Change-Id: Ib201debb338295f3a83bf07f51e0434cd3519db4
Acked-by: Priyadarshini Rajagopal <prajagop@qti.qualcomm.com>
Signed-off-by: Chaitanya Pratapa <cpratapa@codeaurora.org>