Trivial: code simplification, return early

This commit also, (for what it is worth) removes a
difference to the same file in openbsc, which I found
while looking for changes that affected SMPP delivery.
This is essentially a "forward-port" of [1]

[1] https://gerrit.osmocom.org/#/c/openbsc/+/3899/

Change-Id: I350c19f5bb70b2656171c096334c2ee83f49df7e
1 file changed