msm: kgsl: Properly walk the list of timeline signals in a aux command

Commit 36b196ce ("msm: kgsl: Add software timelines") didn't properly
advance the user source pointer while walking the incoming list of timeline
signals in an aux commmand which resulted in only the first listed timeline
getting signaled.

Fixes: 36b196ce ("msm: kgsl: Add software timelines")
Change-Id: Ic0dedbad400f276abea6b368421ccdcef1645b9e
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>