NEEDS TESTS: ail: Handle larger block sizes

We need to support up to 16 bytes/sample * 4 samples/pixel = 64 bytes/pixel for
multisampling to work with formats like RGBA32F.

Fixes dEQP-GLES3.functional.fbo.msaa.4_samples.rgba32f

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>