Small start but useful to collect refactorings/simplifications for
common igt patterns. Please add more if you stumble over some so that
we can occasionally run this to clean up the tests.

I haven't figured out yet how to do the assert_cmpint->assert_eq
transformation.

Run this with

spatch --sp-file lib/igt.cocci --in-place tests/*.c

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>