gem_lut_handle: Make the error checking explicit for LUT handling

gem_lut_handle: Make the error checking explicit for LUT handling

What this test is interested in is the handling of the LUT for very
large arrays, irrespective of whether such batch are actually
executable. So adjust the pass/fail checks to be explicit in the error
they are looking for, so that we do not conflate memory/aperture
pressure as a failure in the LUT API.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=65391
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>