panfrost: Fix incorrect test condition

Oh, the irony. I linked to this file in a software design class as an example of how unit testing works under the hood, since it's not using any particular testing framework. In doing so I realized the test is totally broken. It doesn't matter -- the tests passed before, pass now, and the code being tested is correct. But let's still fix the embarassing logic error for future Panfrost hackers.

Fixes: d42e53c7 ("panfrost: Unit test clear colour packing") Signed-off-by: Alyssa Rosenzweig alyssa@collabora.com