Changes

examples/ipa-stream-client: Fix wrong call to osmo_ipa_process_msg()

The function osmo_ipa_process_msg() is already called internally by the
segmentation callback osmo_ipa_segmentation_cb(), which calls
ipa_check_pull_headers() which in turn calls osmo_ipa_process_msg().

The program was still working because it was using msg->data which isn't
modified by osmo_ipa_process_msg(), but the l2h pointer was incorrectly
modified.

Change-Id: Idec574f59587c681dd059266c9a9cf244bf41dc3